Year 2009 UCD- ITS- RR- 09- 21
2007 Alternative Fuels Incentive Program ( AFIP)
Plug- In Hybrid Electric Vehicle ( PHEV)
Demonstration and Consumer Education, Outread, and
Market Research Program
Principal Investigator: Kenneth S. Kurani
Project Management: Kevin Nesbitt, Marilyn Kempster
Researchers: Jonn Axsen, Nicolette Caperello, Jamie Davies, Tai Stillwater
Plug- in Hybrid Electric Vehicle Research Center
Institute of Transportation Studies
University of California, Davis
June 30, 2009
Conducted under a grant by the California Air Resources Board of the
California
Environmental Protection Agency
Grant Number: G06- AF04
Institute of Transportation Studies ◦ University of California, Davis
One Shields Avenue ◦ Davis, California 95616
PHONE: ( 530) 752- 6548 ◦ FAX: ( 530) 752- 6572
WEB: http:// www. its. ucdavis. edu
i
DISCLAIMER
The statements and conclusions in this report are those of the Grantee and not necessarily
those of the California Air Resources Board or the University of California. The mention
of commercial products, their source, or their use in connection with material reported
herein is not to be construed as actual or implied endorsement of such products.
ii
ACKNOWLEDGEMENTS
This work was funded through the California Air Resource Board’s Alternative Fuels
Implementation Program ( AFIP). Additional funding was provided by the California
Energy Commission’s Public Interest Energy Research ( PIER) Program. AAA Northern
California, Nevada & Utah and Idaho National Laboratory ( United States Department of
Energy) provided in- kind support.
We’d like to thank the thirty- four households who participated in the research reported
here, especially inviting us into their homes multiple times, their willingness to complete
questionnaires and interviews, and their frank evaluations.
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TABLE OF CONTENTS
DISCLAIMER i
ACKNOWLEDGEMENTS ii
LIST OF FIGURES viii
LIST OF TABLES xi
ABSTRACT xii
EXECUTIVE SUMMARY I
Project Design I
1) HEV to PHEV Conversions I
2) Demonstration and Research II
3) Public Education and Outreach II
Research Activities within the Project II
A. Household response to the PHEV- conversions II
B. Narratives III
C. Interfaces and Instrumentation III
D. Social Influence IV
Participating Households IV
What PHEVs do Project Participants Design? V
Charging and Refueling Behaviors VI
Variation in Vehicle Use, Recharging, and CD- miles Across Households VIII
The Overall Effects of Recharging on Energy Use IX
Narrative Analysis: What, why and how? XI
Interfaces and Instrumentation XII
Social Influence on the Evaluation of, and Spread of Information about, PHEVs XIII
iv
1. A RESEARCH AGENDA TO ADDRESS HOW CONSUMERS DRIVE, RECHARGE, AND
VALUE PLUG- IN HYBRID ELECTRIC VEHICLES 1
The Project in Context 2
Reasons for this Project 3
Are Consumers Impediments to PHEV Commercialization and Benefits? 3
Project Design Summary Description 5
1) HEV to PHEV Conversions 5
2) Demonstration and Research 6
3) Public Education and Outreach 7
Research Questions to be addressed in this Project 7
Research Activities within the Project 8
Household response to the PHEV- conversions 8
Narratives 8
Interfaces and Instrumentation 9
Social Influence 10
Defining Terms 11
Basic PHEV Design Concepts 11
2. PHEV DEMONSTRATION AND RESEARCH PLAN 15
Household PHEV Placements 15
Sampling 16
The Interviews and Questionnaires 17
Who are the Project Participants? 24
Gasoline Prices Faced by Survey Respondents and Demonstration Participants 27
Motivations and Knowledge regarding Electric- drive 28
3A. PROJECT RESULTS: PHEV DESIGNS 30
Whose PHEVs? Plausible early markets 30
What PHEVs do they Design? 31
PHEV Design Conclusions 39
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3B. PROJECT RESULTS: RECHARGING 41
How often do People Plug- in their PHEV- conversions? 42
Electricity Availability And Instantaneous Power Demand 45
Electricity Availability & Instantaneous Power Demand: All Weekdays 46
Electricity Availability & Instantaneous Power Demand: Weekend Days 49
Variation in Vehicle Use, Recharging, and CD- miles Across Households 52
The Kermodes 55
The Overall Effects of Recharging on Energy Use 59
Recharging Conclusions 65
3C. PROJECT RESULTS: NARRATIVES 67
Narrative Analysis: What, why and how? 67
What is a Narrative? 67
The Value of Narratives 69
How do We Create Household Narratives? 70
Illustrative Stories from Three Households 71
The Lakes 71
Nancy 74
Octavia 75
Themes from Households’ Narratives 76
Changing Driving Behavior 77
Recharging Habits and Etiquette 78
Confusion 80
Payback 81
Narrative Conclusions 82
3D. PROJECT RESULTS: INTERFACES AND INSTRUMENTATION 84
Interface Details 84
Interface Themes from Household Interviews 90
Limited use of Web Resources 90
Abstract Information 91
Confusion 91
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Novelty 92
Learning from Interfaces 93
Gender Differences 94
Goal Setting 94
Impact of Additional Summary information on Fuel Economy 94
Michael and Cindy Mackson ( 5203) 96
Rick and Samantha Lake ( 6201) 97
Information Interface Conclusions 99
3E. PROJECT RESULTS: SOCIAL INFLUENCE 101
Background 101
Methods: Observing Interpersonal Influence 103
Stage 1: Contact primary household and elicit personal network. 105
Stage 2: Collect baseline information from the personal network. 106
Stage 3: Stimulate personal network with PHEV trial. 106
Stage 4: Network questionnaire and selected interviews. 107
Some Preliminary Results 107
The Noels as electric- drive novices 109
Billy Woods as an electric drive novice with an EV enthusiast in his network 111
The McAdams as pro- societal technology enthusiasts 111
The Rhodes as pro- societal technology enthusiasts with family values 112
Preliminary Discussion and Conclusions 112
4. DISCUSSION AND CONCLUSIONS 118
Putting Discussion and Conclusions in Context 118
Assessing PHEV Purchase Intentions and Design Priorities 120
It ( still) isn’t about all- electric driving; it’s about fuel economy 120
Project results do differ from survey results in some important ways 121
If it’s not about all- electric driving now, can it be in the future? 122
Charging and refueling behaviors 123
Recharging: How often, where, and when 123
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Total Energy, with and without recharging 125
Recharging Habits and Etiquette: Infrastructure isn’t the only barrier 126
No One Misses Refueling with Gasoline 127
Driving behaviors 128
Summary Measures of Driving and Recharging 128
Changing Driving Behaviors through User Interfaces 129
Narrative Themes: Confusion and Payback 130
Confusion 130
Valuing PHEVs: Payback and Intuition 131
Social Influence 131
Five Approaches to Describing Social Interactions 132
Looking Forward 134
REFERENCES 135
ACRONYMS AND GLOSSARY 140
APPENDICES 142
APPENDIX A: HOUSEHOLD FINAL INTERVIEW PROTOCOL 143
APPENDIX B: PHEV BUYERS’ GUIDE ( ON- LINE QUESTIONNAIRE) 147
APPENDIX C: PHEV DESIGN GAMES ( ON- LINE QUESTIONNAIRE) 155
APPENDIX D: CALIFORNIA AND NORTHERN CALIFORNIA SURVEY OVERSAMPLES’
PHEV DESIGNS 155
APPENDIX E: PHEV PROJECT HOUSEHOLDS’ ELECTRICITY AVAILABILITY AND
INSTANTANEOUS POWER DEMAND, DAILY 170
APPENDIX F: THREE PHEV PROJECT HOUSEHOLDS’ NARRATIVES 178
1. Rick and Samantha Lake 178
2. Nancy 189
3. Octavia 197
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LIST OF FIGURES
Figure ES- 1: Electricity Availability ( Percent of PHEVs Plugged- in) and Instantaneous
Power Demand by Time- of- Day ( Watts), Weekday Average. VII
Figure ES- 2: Gasoline- only Fuel Economy by Percentage of Miles Driven in CD Mode,
Weighted by Total Monthly PHEV ( CD+ CS) Distance IX
Figure ES- 3: Decrease in Households’ Total Energy ( Gasoline plus Electricity) for their
PHEV- conversion ( as compared to an HEV) by Percent of Miles driven in CD
Mode, percent. XI
Figure 1: Basic PHEV Drivetrain Options— Series vs. Parallel Design 12
Figure 2: Illustration of Typical PHEV Discharge Cycle ( 65% DOD) 13
Figure 3: Geographic distribution of PHEV Project participants ( n= 34) 17
Figure 4: Screenshot of Development Priority game ( Round Four) 22
Figure 5: Screenshot of Purchase Design game (“ high” price, vehicle model customized
for respondent) 24
Figure 6: Comparing gasoline prices from survey respondents ( lines) and Project
participants ( diamonds) 27
Figure 7: Comparing environmental beliefs among survey respondents (“ CA” and
“ NCA”) and Project participants (“ Demo”) 29
Figure 8: Comparing electric- drive knowledge among survey respondents ( CA and NCA)
and Project participants (“ Demo”): “ From what you understand of these vehicle
technologies, which can use fuel, and which can be plugged in?” 29
Figure 9: Comparing base vehicles chosen for PHEV Purchase Design Game ( plausible
early market only: CA, n= 286; NCA, n= 63; Project, n= 30) 32
ix
Figure 10: Upgrades selected in PHEV design games by Project participants ( plausible
early market Project participants only, n= 28) 33
Figure 11: Distribution of selected PHEV designs in Round Four of Development game
( plausible early market only: Project, n= 28) 34
Figure 12: Distribution of selected PHEV designs in high price scenario of Purchase
Design Game ( plausible early market Project participants only, n= 30) 36
Figure 13: Comparing upgrades selected in Round 4 of Development Priority game,
( plausible early market only: CA, n= 286; NCA, n= 63; Project, n= 28 36
Figure 14: California Distribution of selected PHEV designs in Round Four of
Development game ( plausible early market only: CA, n= 286) 37
Figure 15: Northern California Distribution of selected PHEV designs in Round Four of
Development game ( plausible early market only: NCA, n= 63) 38
Figure 16: Three- Sample Comparison of upgrades selected in higher price scenario of
Purchase Design game ( plausible early market only: CA, n= 286; NCA, n= 63;
Project, n= 30) 38
Figure 17: Mean Daily Household Recharging Frequency Distributions, Weekdays and
Weekend Days, Percent 44
Figure 18: Electricity Availability ( Percent of PHEVs Plugged- in) and Instantaneous
Power Demand by Time- of- Day ( Watts), Weekday Average. 47
Figure 19: Variability of Weekday Electricity Availability by Time of Day, Percent 47
Figure 20: High and Low Weekday Instantaneous Power Demand, Watts 49
Figure 21: Electricity Availability ( Percent of PHEVs Plugged- in) and Instantaneous
Power Demand by Time- of- Day ( Watts), Weekend Day Average. 51
Figure 22: High and Low Electricity Availability by Time of Day: All Weekend Days 51
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Figure 23: High and Low Weekend Days Instantaneous Power Demand, Watts 52
Figure 24: Gasoline- only Fuel Economy by Percentage of Miles Driven in CD Mode,
Weighted by Total Monthly PHEV ( CD+ CS) Distance 53
Figure 25: The Kermodes’ Distance- weighted Gasoline- only Fuel Economy by
Percentage of Miles Driven in CD Mode per Recharging Interval 56
Figure 26: Improvement in Gasoline- only Fuel Economy from CS to CD operation,
percent 60
Figure 27: Decrease in Households’ Total Energy ( Gasoline plus Electricity) for their
PHEV- conversion ( as compared to an HEV) by Percent of Miles driven in CD
Mode, percent. 62
Figure 28: Energy Monitor 85
Figure 29: Consumption Monitor 86
Figure 30: Entry Page 87
Figure 31: Entry Page Energy Use Chart 88
Figure 32: Entry Page Performance Comparison 88
Figure 33: Entry Page Detail Table 89
Figure 34: Trips Tab 89
Figure 35 Change in fuel economy from without- access to with- access to the V2Green
website ( change is represented as the percentage change from the harmonic means
of the first and second phases). 95
Figure 36: Stimulating Social Networks with PHEVs 104
Figure 37: Billy Woods’ Sociogram 108
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LIST OF TABLES
Table 1: Upgrades for PHEV Development Priority game 21
Table 2: Price of upgrades for Purchase Design game 23
Table 3: Comparing Project participants, survey respondents, and the general population
26
Table 4: Aggregate Measures of the Kermodes’ Actual and Constructed Months of PHEV
Driving and Recharging 58
Table 5: Energy Use and Savings, sorted by Percent Decrease in Total PHEV Energy Use
64
Table 6: Conceptualization of PHEV attributes ( hypothetical examples) 102
Table 7: Summary of primary households and secondary participants in the personal
network study to date 110
xii
ABSTRACT
Will people recharge a vehicle that does not have to be recharged? This, and the degree to
which plug- in hybrid electric vehicle ( PHEV) designs emphasize gasoline or electricity,
are central to assessing the energy and environmental effects of PHEVs. Plug- in
conversions of hybrid vehicles are being made available to ( predominately new- car
buying) households throughout the Sacramento region for four to six weeks each. The
vehicles are instrumented to report travel and energy; households are interviewed and
surveyed. Results from the first 34 households— all selected in part because they can
recharge a vehicle at home— indicate that on average they will recharge a PHEV about
once per day, but with wide variation across households. The PHEV designs created by
these households emphasize increased fuel economy rather than all- electric operation— as
did the designs of prior representative samples of new- car buyers ( who had not driven
PHEVs). This result may be due in part to 1) “ anchoring” ( respondents are driving a
PHEV that does not practically allow all- electric operation), and 2) households not
creating integrated assessments of gasoline and electricity use/ cost from the in- vehicle
and internet- based instrumentation. Over the PHEV trials, narratives are co- authored
about the PHEVs and their place in the ongoing life- stories of the participants. The
primary themes to emerge are changing driving behavior, recharging habits and etiquette,
confusion about PHEVs and how they work, and the role of payback analyses and more
intuitive assessments of whether PHEVs are “ worth it.” Tracing social interactions by the
participants about the PHEVs reveals that complex translation of ideas and information
about PHEVs is occurring as the PHEV drivers, in particular, use their trial period to
reflexively explore lifestyle and identity possibilities of these new vehicles.
I
EXECUTIVE SUMMARY
This document reports on a research project designed to address the question, “ Why
would consumers buy plug- in hybrid electric vehicles ( PHEVs)?” With funding from the
California Air Resource Board’s Alternative Fuels Implementation Program ( AFIP) and
funding and in- kind support from other partners, the Plug- in Hybrid Electric Vehicle
Research Center ( PHEV Center) at the University of California, Davis implemented a
PHEV Demonstration and Consumer Education, Outreach, and Market Research Project
( hereafter referred to as the Project). This report describes the Project and summarizes the
findings from the first thirty- four households. The Project will continue through 2009;
results will be updated in subsequent reports.
Project Design
The Project was conducted as the following three main activities: 1) vehicle conversion
to plug- in operation, 2) demonstration and research, and 3) education and outreach.
1) HEV to PHEV Conversions
Toyota Priuses were purchased and converted to plug- in operation using the Hymotion,
( now, A123Systems) conversion package. A dozen such vehicles are regularly used in
active support and conduct of the Project. The A123Systems conversion involves the
installation of a 5KWh ( nominal) lithium- ion battery in the spare tire well in the rear
cargo area of the vehicle, as well as the necessary electrical and communications
connections to incorporate the battery into the vehicle’s drive system and to recharge the
battery. The battery charges from a standard US three- prong, grounded, 110- volt outlet.
Using the PHEV terminology in this report, the PHEV- conversions used in this Project
can be described as blended PHEV- 30s, in which we adopt the definition of CD range as
the distance at which the vehicle switches from CD to CS operation. This characterization
will be restated in the discussion of the households to reflect their on- road performance in
these vehicles.
II
Additionally, the vehicles were equipped with onboard data collection and transmission
devices. Idaho National Laboratory ( INL) provided the devices and the cellular service to
transmit the data. V2Green, Inc. ( now, Gridpoint, Inc.) manufactured the data collection
and transmission systems. They also summarize vehicle data on a website; UC Davis
contracted for additional programming services to allow individual Project drivers to
track their performance.
2) Demonstration and Research
The PHEV- conversions have been, and continue to be, placed in households in northern
California for several weeks at a time. Households are recruited with the assistance of
AAA Northern California, Nevada & Utah. During the households’ PHEV trial use
periods, we collect data on travel, vehicle recharging and refueling, performance of the
vehicle, and participants’ response to the PHEV technology. Data are collected directly
from the vehicle using on- board data systems, as well as from interviews, questionnaires,
and fueling logs. 1
3) Public Education and Outreach
The PHEVs were also used in a public education and outreach programs. The vehicles
were displayed at public events and used in educational settings. Information on PHEVs
remains accessible from the PHEV Center’s website.
Research Activities within the Project
Within the overall Project there are four related research activities.
A. Household response to the PHEV- conversions
In some sense the entire Project is about household response to PHEV- conversions. This
specific activity focuses on the following results:
1 We can infer from vehicle data when it has been refueled with gasoline, but the only way to know how
much was paid for gasoline is to have drivers record this information.
III
1. What are the PHEV designs created by Project households and how do these
designs compare to those created by survey respondents who have no experience
driving PHEVs?
2. What are the recharging behaviors of the Project households, and how do driving
behaviors influence recharging behaviors?
3. Given that Project participants are driving one specific incarnation of what a
PHEV can be, what are the effects on their transportation energy use?
B. Narratives
We employ narrative research methods in this Project both to synthesize the large
amounts of disparate data we are collecting for each household and to analyze both those
synthesis documents and the original textual data from the household interviews. The
purpose of the synthesis narratives is to tell the best possible story about each household
and their experience with PHEVs. The purpose of subjecting the interviews to analysis is
to ascertain what themes emerge across the households’ experiences.
C. Interfaces and Instrumentation
Research on driver feedback is carried out in two phases. First, we assess the participants’
use of and response to the in- vehicle energy information displays based on the stock
Toyota Prius Energy Monitor and Fuel Consumption displays ( as modified by the PHEV-conversion)
and the website displaying summary performance data from their vehicle.
Results from this first phase of interface and instrumentation research are included in this
report.
The second phase of instrumentation research builds on the first, but is not scheduled to
begin until summer 2009. In the second phase, a custom- made driver feedback display
will be included as part of the research design for a subset of the Project households.
IV
D. Social Influence
A sub- group of 10 to 15 social networks ( each centered on a household driving the
PHEV- conversion) will be investigated to ascertain how interpersonal interactions
influence assessment of electric- drive vehicles. Analysis of four networks has been
completed to date and is discussed in this report. Three research questions are addressed:
1. Do interpersonal interactions play a significant role in the assessment of electric
drive vehicles?
2. If so, how can we characterize the interpersonal interactions that influence
consumer perceptions of functional, symbolic, and pro- societal attributes?
3. Under what conditions might households adopt the pro- societal car?
Participating Households
Participants are recruited through an “ illustrative” sampling method ( Turrentine and
Kurani, 2007.) Such a sample does not attempt to be representative of a population;
rather, the purpose is to illuminate the behavior of specific groups. The sampling frame
for the Project is defined by 1) automotive insurance requirements, 2) geographic
location, 3) vehicle ownership, 4) driving behavior, and 5) broad categories of household
structure. Participants are selected for the Project with the participation of AAA Northern
California, Nevada & Utah. Volunteers from the recipients of the invitation letter log- on
to a website hosted on a UC Davis server, where they complete a brief questionnaire
which solicits more specifics of the potential participants vehicles, home, travel,
household, and contact information. UC Davis researchers review the questionnaire
responses and select households based on the goal to illustrate the responses of different
types of households.
In comparison to samples of the general population and of the population of California
and northern California who have previously completed questionnaires for UC Davis
regarding PHEVs ( Axsen and Kurani, 2008), the Project households differ in that, on
average, they have higher income, education, and likeliness to own their home. All three
V
of these may be explained by a single design choice made for the Project: all participating
households must have a place to recharge the vehicle at home. Still, the Project
participants as a group only accentuate differences between our prior samples of new- car
buying households and the general population; they do not introduce any new
differences. In particular, the Project participants are similar to other recent samples of
new car buyers in terms of concerns with environment and energy and knowledge about
electric- drive vehicles.
What PHEVs do Project Participants Design?
At the end of their PHEV trial period, households complete a set of PHEV design
games— the same design games completed by prior samples of survey respondents
( Axsen and Kurani, 2008). The overarching conclusion from the design games is that
even the Project households who have had a chance to drive a PHEV ( that offers blended
CD operation) do not design PHEVs that offer all- electric operation. Rather, the Project
participants, like the survey respondents before them, create designs that emphasize
improvements in ( CD and CS) fuel economy.
Project participants who had driven a ( blended- operation) PHEV for a month were more
likely than the previous survey respondents to 1) design a PHEV they are interested to
buy rather than opt to buy a conventional vehicle, 2) design a PHEV that had better
PHEV performance than the base PHEV design offered to them ( the base offering took
eight hours to recharge, achieved 75 mpg in blended CD operation for 10 miles, and
achieved 10 mpg higher in CS operation than a conventional version of the same car),
and 3) choose an HEV as the base vehicle they considered for redesign as a PHEV. The
Project does appear to have a slightly greater persuasive effect in convincing participants
that a PHEV is a worthwhile and desirable vehicle for their household. Still, these
differences are at the margin, and the overall conclusions one draws from the Project
participants are similar to those we drew from the survey.
VI
Charging and Refueling Behaviors
There may be no more fundamental question about PHEVs than whether or not people
will plug- in a vehicle that does not have to be plugged- in. The answer from the Project
participants to date is, “ Yes, we will.” The Project households, on average, plugged- in
these PHEV- conversions about once per day, and did so more often on weekdays than
weekend days. There was large variation in the mean frequency of PHEV recharging
across households— from zero to 2.6 times per weekday and zero to 1.5 times per
weekend day. The mean frequency of plugging- in on weekend days was lower than on
weekdays because there was now workplace charging and the PHEVs were more likely
to be away from home, and thus away from the households’ primary or sole recharging
location. Only a few households found away- from- home recharging locations they used
on a regular basis. The incidence of zero charging on weekdays is largely explained by
one household who decided that recharging the PHEV- conversion made too little
difference to warrant their difficulty and hassle in recharging the vehicle.
We assess the time- of- day distribution of PHEVs’ access to electricity and actual
electricity demand to recharge PHEVs. The former is the distribution of times that
PHEVs are plugged into the grid; the later is the distribution of times that electricity is
actually being demanded by PHEVs for recharging. The weekday distributions from the
last week of each of the 34 households are shown in Figure ES- 1.
Across the 170 weekdays represented in Figure ES- 1 ( 34 households times 5 weekdays),
70 percent of households had plugged in their PHEV between 10: 00 pm and 6: 00 am. By
9: 00 am only 20 percent of households had their PHEV connected to the grid. This can be
explained by the number of respondents in the Project that have full time jobs, and
typically leave home in the morning to go to work. While there were two households that
charged during the day while at work, the PHEVs that were plugged- in to the electrical
grid during midday were mostly due to retired individuals and teleworkers. At 4: 00 pm,
when households start to return home from work, vehicles begin to be plugged in, until
10: 00 pm by which time the percentage of households who have plugged in their PHEV
stabilizes again at about 70 percent.
VII
Figure ES- 1: Electricity Availability ( Percent of PHEVs Plugged- in) and
Instantaneous Power Demand by Time- of- Day ( Watts), Weekday Average.
Given driving and recharging behavior by the Project households, electricity demand to
recharge their vehicles ramps up at 5: 00pm and peaks just after 10: 00pm. It declines
steadily through the rest of the night and into the morning, reaching practically zero by
5: 00am. While there were several households that charged during the day at work, most
of the demand to recharge these vehicles was between 9: 00am and noon.
Weekend days differ from weekdays. Fewer PHEVs are plugged in during the weekend
high availability period: about 55 percent of vehicles were plugged in between 11: 00pm
and 6: 00am on weekends as compared to 70 percent between 10: 00pm and 6: 00am
weekdays. The weekend high availability period starts an hour later than on weekdays.
Compared to weekday recharging, it appears as though some individuals, if they had
access to an outlet, plugged in longer during the weekend. However, on average, not as
many people plugged in their vehicles on weekend days compared to average weekdays.
As with weekday electricity demand, most actual weekend electricity demand to recharge
the vehicles occurred between 5: 00pm and 2: 00am. There are significant differences in
the total power required between weekdays and weekend days. On average, weekend
electricity demand increased more slowly over the course of the evening. In general, this
VIII
difference from weekdays is because during weekends the PHEVs are starting their
recharging at a higher state of charge than on weekdays, and, thus, there is not as great a
cumulative impact upon the power demanded. Essentially, as those vehicles plugged in
later start recharging, their impact on the rate at which total power demand increases
( summed across all households) is less than on weekdays, because other households’
vehicles which were plugged in earlier have already finished recharging.
Variation in Vehicle Use, Recharging, and CD- miles Across Households
The recharging results presented so far focus on the recharging behavior summed and
averaged across the participants. This hides the variation in 1) the frequency with which
people recharged the PHEV, 2) the distances households drive per recharging interval,
i. e., the distance driven between two recharging events, and 3) the percentage of total
miles each household drove in CD mode. The participants varied in their experiences
with the vehicle, in their concepts and appreciation of the value of recharging, and in
their access to different recharging locations. Figure ES- 2 illustrates the overall
variability in performance of the participants with regard to their average monthly
( gasoline- only) fuel economy, the percentage of miles they drove in CD mode, and the
overall distance they drove in the PHEV during their respective vehicle trials. 2
In Figure ES- 2, each circle represents one household. The diameters of the circles are
proportional to the total miles driven by that household in the PHEV over their trial
period. For scale, the largest circle (“ Nancy,” in the lower left) represents just over 3,000
miles of driving. That it also depicts the lowest percentage of miles in CD mode and
nearly the worst gasoline- only fuel economy in the trial to date is due to several long,
multi- day tours Nancy took away from home during which she drove the PHEV-conversion
many miles between recharging events.
The basic conclusions to be drawn are that individuals varied greatly in their driving and
recharging behaviors and, importantly, in the relationship between these two. A few
households drove only 20 to 30 percent of their miles in CD mode. On the other hand, a
2 All household names are pseudonyms.
IX
few households drove approximately 80 percent of their miles in CD mode and achieved
monthly average gasoline- only fuel economy measures of approximately 70 mpg.
Figure ES- 2: Gasoline- only Fuel Economy by Percentage of Miles Driven in
CD Mode, Weighted by Total Monthly PHEV ( CD+ CS) Distance
Figure ES- 2 shows the potential for drivers of these particular PHEV- conversions to
achieve reductions in the gasoline- intensity of their daily mobility through differences in
how they drive and recharge the vehicle, e. g., driving and recharging such that the miles
in a recharging interval closely match the driver’s realized CD range. Still, there is
tremendous variability in how closely participants’ behavior matches this technically
ideal pattern that is not illustrated in Figure ES- 2.
The Overall Effects of Recharging on Energy Use
First, we address changes in gasoline- only fuel economy because this was the primary
metric used by households; we then turn to an analysis of the total energy effects. Across
the group of households, mean CS fuel economy was 44.7mpg; mean CD fuel economy
was 67.1mpg. Thus, the group mean increase in CD vs. CS is 49 percent. These group
measures mask tremendous variation across households. The distribution of households’
mean fuel economy improvements between CS and CD operation ranged from 21 to 101
0
20
40
60
80
100
0% 20% 40% 60% 80% 100%
Miles Driven in CD Mode, Percent
Kermode Lakes Nancy Octavia All other Households
X
percent. However, improvements over 70 percent were exceptions— 90 percent of
households had improvements less than 71 percent and the median improvement was 46
percent.
The analysis of total energy effects presented here is preliminary and partial. It is
preliminary because we do not expect that the full range and variety of the relationships
between travel and recharging behavior on one hand and total energy use on the other
have yet been observed among the Project participants’ to date. Further, this analysis is
preliminary because only one particular PHEV is analyzed. The analysis is partial
because it is not a life- cycle analysis; here we address only electricity out of the battery
and gasoline out of the tank. Further, the analysis is partial because we address only the
marginal difference that it makes that the Project households drove and recharged ( to the
extent each did) a PHEV instead of an HEV.
We compare their total energy use, i. e., gasoline plus electricity, during their PHEV trial
to the amount of gasoline they would have used had they driven their entire PHEV trial
without ever recharging. To illustrate relationships between driving, recharging, and
energy use we plot the marginal percentage decrease in total gasoline ( tank to wheels)
plus electricity ( battery to wheels) by the percent of their miles they drove in CD mode
for their four- week PHEV trial in Figure ES- 3. As in Figure ES- 2, the size of each data
point in Figure ES- 3 is proportional to the total miles driven during each household’s
trial.
The first point is that a comparison of Figures ES- 2 and ES- 3 shows the households’ use
of the simple measure of ( gasoline- only) fuel economy is not qualitatively wrong. As the
percent of miles driven in CD mode increases, fuel economy and energy savings both
increase. Figure ES- 3 confirms that across the households, energy was being saved
through the substitution of electricity for gasoline by recharging the PHEVs compared to
the amount of gasoline these households would have consumed had they not recharged
the PHEVs.
The relatively low percentage of CD driving of Nancy and the Kermodes— which we
know was due to long, multi- day tours— yields low percentage energy savings from a
XI
large ( compared to the other households) base. Octavia and the Lakes achieved much
higher percent energy reductions but across much less travel, and thus a smaller energy
base. They did so in part because of the much higher percentage of their travel they
accomplished in CD mode— accomplished both because they recharged more often and
traveled fewer miles than Nancy and the Kermodes.
Figure ES- 3: Decrease in Households’ Total Energy ( Gasoline plus
Electricity) for their PHEV- conversion ( as compared to an HEV) by Percent
of Miles driven in CD Mode, percent.
The range of percent total energy savings achieved by plugging in the PHEV- conversions
in comparison to not plugging them in is from - 1 to 19 percent. Higher percent savings
are achieved by households who drive higher percentages of their miles in CD
operation— either because they tend to drive fewer miles per day than their achieved CD
range ( and generally recharge everyday) or recharge multiple times per day. The
household in which energy use increased was due to changes in drivers and trip distances.
Narrative Analysis: What, why and how?
We have two purposes in employing narrative: synthesis and analysis. First, we have a
tremendous amount of disparate information about each household; narrative provides a
framework to organize, analyze, and report all these data. Second, narratives explain,
provide coherence, and show causality.
 


 
 
 
 
        	   
      
                          
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XII
The primary themes to emerge from the narratives are changing driving behavior
( primarily through the influence of the in- vehicle instrumentation), recharging habits and
etiquette, confusion about PHEVs and how they work, and the role of payback analyses
or more intuitive assessments of whether PHEVs are “ worth it.” Some people changed
how they drive the car after seeing their instantaneous fuel economy; others drove the
PHEV as any other car, and specifically like they had no particular control over energy
use. Some people likened plugging in the PHEV to recharging a cell phone and made it
part of their daily routine, but were hesitant to recharge outside of their homes due to a
lack in social etiquette and concerns for safety. Many people were confused about the
state of charge of the battery; this influences how often they recharged. Some were
concerned about the cost of the PHEV and payback; they saw PHEVs as helping with
environmental problems but wondered how much they were paying to do so.
Interfaces and Instrumentation
There are two main sources of vehicle information available to study participants. First,
there is the stock display console screen in the 2007 and 2008 model Toyota Priuses
converted to PHEVs for the Project. The two screens are 1) an Energy Monitor schematic
of energy flows in the vehicle as well as the instantaneous fuel economy, and 2) a
Consumption screen that provides fuel economy averaged over 5- minute intervals and
over the tank ( or whenever the driver resets the average).
Second, participants had access to the data they generated through driving, recharging,
and refueling the vehicle via a website designed by the on- board data system provider.
The website displays vehicle summary data as well as the location and status of the
vehicle. Although the website provides detailed summary information— for example,
driving data are summarized by trip, day, week, fortnight, and month— few participants
reported being influenced by the website.
The discussion of interfaces and feedback during interviews was subjected to additional
analysis. The resulting themes were limited availability of web- based interfaces,
information presented in abstract contexts, confusion ( either about what certain
information meant or about what behaviors to enact based on given information), novelty
XIII
or lack of persistence of attention to information and new behaviors, learning, goal
setting, and an hypothesis about gender- specific responses to energy information. The
following lessons from these themes are proposed to guide further research into the role
of interfaces and instrumentation:
• The closer information is to the point of interest and action, i. e. in the car vs. on
the home computer, the more likely it is that the information will be used.
• Simplicity in representation and interpretation is critical to driver understanding.
• The interface should support drivers in setting and achieving goals by providing
relevant summary information.
• Instantaneous Fuel Economy can provide drivers with erroneous information,
especially during braking.
• Whenever possible, information should be presented in a grounded context so that
drivers can quickly understand the relative impact of their behavior.
Social Influence on the Evaluation of, and Spread of Information about,
PHEVs
PHEVs and other electric- drive vehicles are innovations because of what they can do:
new battery and drivetrain technology allows users to offset gasoline use with electric-drive
capabilities and to plug- in to the electrical grid, often at home. From a functional
perspective, consumers may interpret the desirability of electric- drive technology
according to its ability to save them money on transportation, to improve drivetrain
reliability, or to simply improve the experience of driving. But PHEVs, and electric- drive
vehicles more generally, may also be assigned different social meanings than
conventional vehicles. For example, Heffner et al. ( 2007) found five symbolized
meanings that motivated HEV purchases: preserve the environment, oppose war, manage
personal finances, reduce support to oil producers, and embrace new technology. Further,
electric drive vehicles embody another class of attribute that differentiates them from
conventional vehicles: the potential to benefit society in new ways. Green ( 1992, p133)
XIV
provides a framework to classify goods on a private/ public scale, where private good are
characterized by “ exclusive and personal consumption and individual payment; not
associated with the public welfare,” whereas societal or public goods are characterized by
“ nonexclusive consumption and collective payment” such as “ clean air” and “ saving
endangered species.”
The first question in this social network research asks whether interpersonal influence
plays a significant role in the assessment and adoption of electric- drive vehicles. The
research reported here suggests that the observed social interactions are influential for
primary households ( those actually driving the PHEV- conversions) and secondary
participants ( members of primary households’ social networks who have volunteered for
interviews). The second research question delves deeper to explore and characterize
specific processes of social interaction and influence. We describe these interactions from
five perspectives: contagion, conformity, dissemination, translation, and reflexivity. The
primary households and their interaction with their social network illustrate ( to some
degree) each of these five approaches. We find the two most insightful approaches to be
translation and reflexivity.
Results to date suggest that interpersonal interactions within social networks play an
important role in shaping the assessment of these PHEV conversions, and likely electric-drive
vehicles more generally. Diffusion, conformity, and dissemination provide useful
concepts for particular processes, but translation and reflexivity appear to best provide
the language and theoretical depth required to integrate the various motives and
perceptions observed among participating social networks. However, before conclusions
can be drawn, more networks need to be explored and further analysis is required.
1
1. A RESEARCH AGENDA TO ADDRESS HOW CONSUMERS DRIVE,
RECHARGE, AND VALUE PLUG- IN HYBRID ELECTRIC VEHICLES
This document reports on a research project designed to address the question, “ Why
would consumers buy plug- in hybrid electric vehicles ( PHEVs)?” An integrated set of
demonstration, research, education, and outreach activities was deployed to accomplish
the following:
• Provide California households with the requisite knowledge and experience to
provide informed responses to PHEVs, thus overcoming one primary impediment
to commercialization— a lack of understanding by consumers, vehicle designers,
fuels providers, and regulators of consumers response to the following:
o Driving, recharging, and refueling patterns of PHEVs, that is, to what
extent will drivers of PHEVs recharge from the grid or refuel the ICE,
and where and when will recharging occur;
o Different symbols of the meaningful and motivational features and
capabilities of PHEVs, e. g., all- electric range, high fuel economy,
electric- drive, ability to use renewable fuels, etc.;
• Inform the California Air Resources Board of the potential effect of consumer
driving and recharging/ refueling behavior on the potential for PHEVs to reduce
greenhouse gas and other vehicle emissions.
• Inform the California Air Resources Board as well as the California Energy
Commission, electric utilities, CalISO, and other parties of consumer response to
PHEVs on the potential benefits, markets and impacts of PHEV technologies,
including the following:
o The potential for PHEVs to reduce petroleum consumption;
o The effects of PHEVs on operation of the electrical grid;
With substantial funding from the California Air Resource Board’s Alternative Fuels
Implementation Program ( AFIP) and additional support from the California Energy
2
Commission’s Public Interest Energy Research ( PIER) Program, the Plug- in Hybrid
Electric Vehicle Research Center ( PHEV Center) at the University of California, Davis
implemented a PHEV Demonstration and Consumer Education, Outreach, and Market
Research Project ( hereafter referred to as the Project). Other Project contributors include
the AAA Northern California, Nevada & Utah, and Idaho National Laboratory ( United
States Department of Energy).
This report describes the Project and summarizes the findings from the first thirty- four
households. The Project will continue through 2009; final results will be updated in
subsequent reports.
The Project in Context
The Project is the third research activity in a multi- year, integrated research agenda. In
brief, the agenda is as follows:
1. PHEV “ pioneers”— interviews of early converters of HEVs to PHEVs and drivers
of these first conversions
2. Internet- based survey of new car buyers’ baseline knowledge and priorities
regarding PHEVs— samples representative nationally, with over- samples to
represent new car buyers in California and northern California.
3. Household PHEV Demonstration and Market Research
a. Add improved in- vehicle energy feedback displays of cost, integrated
feedback on electricity and gasoline use, emissions etc.
4. A second large sample survey based on the prior PHEV research projects
The first two research activities in this agenda are completed, the third is described in this
report as are initial findings, and the fourth is forthcoming pending funding. As
appropriate, the description and reporting of the design and results of the Project will be
put into context of this larger agenda. For examples, some of the questionnaires
completed by Project participants are the same as those completed by the participants in
3
the prior national survey and the Project participants are compared to the northern
California over- sample.
Reasons for this Project
This Project addressed the following questions: how will drivers use PHEVs— drive,
recharge, and refuel them— and what kinds of PHEVs will buyers want? The defining
feature of PHEVs— the ability to plug the vehicle into the electrical grid and refuel it
from another network of liquid ( or gaseous) fuels— is the source of both their potential
benefits and the uncertainty over whether their potential can be realized. Much of the
appeal of PHEVs is based on the flexibility afforded by two energy systems. This
flexibility offers new choices for consumers, from a range of vehicle designs, e. g., size of
battery and motor, as well as flexibility around the way the vehicle is used, e. g., how
often the battery is recharged vs. how often the liquid ( or gaseous) fuel is refueled. To
achieve and optimize the potential of PHEVs to reduce vehicle emissions and gasoline
consumption, i. e., to accomplish their societal benefits, PHEV owners will need to use
electricity from the grid.
Consumers will be faced with a previously unknown set of capabilities and thus
unfamiliar choices. For example, the larger the battery chosen by buyers, the greater the
percentage of their driving can be accomplished using electricity from the grid. On the
other hand, the larger the battery the higher the initial price of the vehicle. As the initial
vehicle price will be readily apparent, but the new and largely unfamiliar benefits only
unfold in the future, sound policy and market actions depend on assessing potential
consumers’ response to these distributions of costs and benefits. Moreover, PHEVs can
be engineered to suit different consumers or regulators; PHEVs can be designed to
minimize CO2 reduction, provide high torque and acceleration, maximize battery life, or
maximize consumer control over the choice between electricity and gasoline.
Are Consumers Impediments to PHEV Commercialization and Benefits?
Are PHEVs to be encouraged because they represent a rich set of consumer and social
values or discouraged as inviting unwelcome, unproductive tradeoffs between the here-
4
to- fore largely separate gasoline and electrical energy systems? One key variable in
PHEV commercialization and in the attainment of any environmental and social benefits
is the “ locus of control,” that is, who has control over vehicle operations— drivers,
vehicle engineers, or regulators?
The fear of regulators, vehicle manufacturers, and energy suppliers is that drivers- in-control
could be deleterious to goals for the environment, air quality, energy
consumption, energy systems operation, and the ability to warrant vehicles for emissions,
fuel consumption, and reliability. In this worldview consumers are seen as at best
disinterested and non- compliant, and at worst as anti- compliant. This bias is old and
persistent; we believe it may be contradicted by a number of real world experiences.
Writing a review of consumer energy research nearly three decades ago, McDougall et al
( 1981) reveal such bias: “… recognize that probable energy savings represents a net
impact based on potential savings in a technical sense, reduced to allow for imperfect
behavioral response.” [ Emphasis in the original.] More recently, Friedland et al. ( 2003)
observe the continued absence of people in energy policy: “ Especially lacking is policy
or guidance that incorporates personal choices in energy– use reduction decision- making.”
What this pessimistic view of people ignores is that at least some people if provided with
control, information, incentive, and opportunity— such as can be provided with a
PHEV— will exceed the “ technical potential” possibilities. In interviews with buyers of
non- plug- in HEVs, we have heard several accounts that suggest their drivers were saving
more energy than technical analysts would calculate ( Kurani and Turrentine, 2004;
Heffner, Kurani, and Turrentine, 2005). This occurred by several means that illustrate the
potential effects of driver control, information ( feedback), incentive ( symbolic and/ or
financial), and opportunity. In some cases, the HEV prompted further thinking by the
owner about energy reductions in other areas of their life. Most directly ( and in
contradiction to economists’ assumptions of a rebound effect, i. e., increased driving
because of reduced operating costs), some HEV drivers actively attempted to drive their
HEV less than the vehicle it displaced. In gaming interviews with non- BEV owners we
observed that when provided with an incentive in the form of a cost savings through the
use of electricity rather than gasoline, these households appeared to quickly learn to
5
adjust their travel between the use of a ( hypothetical) BEV and their actual vehicles
( Kurani and Turrentine; 1996, 2002).
Project Design Summary Description
This discussion points to two facts that guide the design of this Project. First, consumers
are unaware of the potential advantages, disadvantages, new capabilities, and costs of
PHEVs. Second, how consumers form their awareness, how they assimilate and process
new knowledge about PHEVs, how they turn this awareness, knowledge, belief, and
motivation into demand for PHEVs, and thus whether consumers will buy PHEVs, which
type of PHEVs they would like to buy, and how they might drive, recharge and refuel
those PHEVs are all largely unknown.
The Project was conducted as the following three main activities.
1) HEV to PHEV Conversions
With funding from the California Air Resources Board, Toyota Priuses were purchased
and converted to plug- in operation using the Hymotion, ( now, A123Systems) conversion
package. While such vehicle conversions are clearly only an interim step, they offer a
test- bed for real world research with car- buyers. A dozen such vehicles are regularly used
in active support and conduct of the Project. Another Prius ( purchased with funding from
the California Energy Commission) was converted, adorned with large signs identifying
it as a PHEV and as a vehicle of UC Davis’ PHEV Research Center; this vehicle is
reserved for education and outreach activities and support of the Project.
The A123Systems conversion involves the installation of a 5KWh ( nominal) lithium- ion
battery in the spare tire well in the rear cargo area of the vehicle, as well as the necessary
electrical and communications connections to incorporate the battery into the vehicle’s
drive system and to recharge the battery. The battery charges from a standard US three-prong,
grounded, 110- volt outlet. The recharging point is in the left- rear bumper of the
vehicle. A fully discharged battery can be recharged in approximately five hours.
6
It is important to understand that the converted vehicle remains subject to the underlying
control strategy of the OEM vehicle. Specifically, these PHEV- conversions are best
described as operating in a manner that more or less continuously blends electricity and
gasoline— though it is the case that while the conversion, or supplemental, battery is
discharging, far more electricity is being used than in a conventional Prius and it is easier,
though by no means easy, to drive so that the ICE remains off. Still, even while the
supplemental battery is contributing to the propulsion of the vehicle, aggressive
accelerations, speeds higher than 35mpg, and upward grades are likely to cause the ICE
to start to meet the additional load.
Additionally, the vehicles were equipped with onboard data collection and transmission
devices. The devices and the cellular service to transmit the data were provided to the
Project by INL. V2Green, Inc. ( now, Gridpoint, Inc.) manufactured the data collection
and transmission systems. They also port the data to a website that summarizes vehicle
performance. UC Davis contracted for additional programming services to allow
individual Project drivers to track their performance. These information systems and
modifications will be described further in section 3D: Instrumentation and Interfaces.
2) Demonstration and Research
The PHEV- conversions have been, and continue to be, placed in households in northern
California for several weeks at a time. Households are recruited with the assistance of
AAA Northern California, Nevada & Utah. The households are selected because they
represent important markets segments and use patterns for PHEVs. The realized sample
of Project participants to date will be described in detail in the next section. During the
households’ PHEV trial use periods, we collect data on travel, vehicle recharging and
refueling, performance of the vehicle, and participants’ response to the PHEV
technology. Data are collected directly from the vehicle using on- board data systems, as
well as from interviews, questionnaires, and fueling logs. 3
3 The demonstration vehicles are instrumented to record travel and recharging/ refueling behavior.
Additionally, drivers complete a refueling log: we can infer from vehicle data when it has been refueled
7
3) Public Education and Outreach
The PHEVs were also used in a public education and outreach programs. The vehicles
were displayed at public events and used in educational settings. Information on PHEVs
was accessible from the PHEV Center’s website. Education and outreach events included
UC Davis’ Picnic Day and Whole Earth Festival, Earth Day activities, and other public
events, school events, and vehicle displays.
Research Questions to be addressed in this Project
The Research and Education and Outreach activities address the following questions.
• Purchase choices:
• What sorts of PHEV designs will buyers want?
• Charging and refueling behaviors:
• When, where and how much will PHEV owners choose to recharge from
the electrical grid rather than refuel with liquid ( or gaseous) fuels?
• Driving behaviors:
• When, where and how much of their driving will PHEV users accomplish
by electricity vs. gasoline?
• How does energy use and cost information affect driving and recharging
behavior?
• Broader impacts:
• How will overall social and environmental benefits affect individual
choices?
• What information about PHEVs is spread through the social networks of
participants and how do those exchanges affect the formation of drivers’
values regarding PHEVs?
with gasoline, but the only way to know how much was paid for gasoline is to have drivers record this
information.
8
Research Activities within the Project
Within the overall Project there are four related research activities, these are briefly
described here and more fully discussed in the following major sections of this report.
Household response to the PHEV- conversions
In some sense the entire Project is about household response to PHEV- conversions. This
specific activity focuses on the following results:
1. What are the PHEV designs created by Project households and how do these
designs compare to those created by survey respondents who have no experience
driving PHEVs?
2. What are the recharging behaviors of the Project households, and how do driving
behaviors influence recharging behaviors?
3. Given that Project participants are driving one specific incarnation of what a
PHEV can be, what are the effects on their transportation energy use?
The other activities described next explore why the responses above are as they are, how
they are formed, and how they might be influenced by information.
Narratives
We employ narrative research methods in this Project both to synthesize the large
amounts of disparate data we are collecting for each household and to analyze both those
synthesis documents and the original textual data from the household interviews. Each
household completes three on- line questionnaires including two sets of complex PHEV
design games. Each household completes three to five semi- structured interviews,
resulting in two to six hours of recorded and transcribed conversations. Each vehicle is
equipped with on- board data collection systems, resulting in 500,000 to 700,000 records
on the household’s driving, recharging, and refueling of the vehicle. Synthesis narratives
are written by incorporating data from all these sources. Narratives have beginnings and
ends, but are more than simple chronologies of events; they have plots to give meaning
9
and coherence to events. The starting point for synthesizing the data into a narrative
begins with the interviews. Additional data are brought in from the questionnaires, e. g.,
the PHEV designs created in the on- line questionnaires. The interviews explain why the
households designed the PHEV they did, supported ( or contradicted, if that is the case) by
the data from the vehicle.
The purpose of the synthesis narratives is to tell the best possible story about each
household and their experience with PHEVs. The purpose of subjecting the interviews to
analysis is to ascertain whether themes emerge across the households. That is, what can
we say about the groups’ experience? For example, across the group how do households
talk about similar things, e. g., recharging?
Both the synthesis narratives and the interview analyses are somewhat contrived since, in
general, the entire Project is an intrusion into the participants’ ongoing lives ( narratives)
and specifically, the interviews are semi- directed and therefore not entirely of the
households’ own telling. For example, knowing that recharging behavior is central to the
research goals of the Project, all households are asked to talk about recharging. We
neither simply wait to listen to whether they talk about recharging, nor allow them to
complete their interview without at least addressing questions about recharging.
Interfaces and Instrumentation
Research on the effect of driver feedback is carried out in two phases. The first is integral
to the design of the vehicles, PHEV- conversions, and on- board data systems deployed in
this Project. The PHEV- conversion process adds a color change to the battery icon on the
stock Prius Energy Monitor to tell the driver when the vehicle has switched from CD to
CS operation. 4 The on- board data systems transmit data to the service provider, who
displays summaries of the data on a website. As part of the household interviews, we
assess the participants’ use of and response to these two interfaces. Further, we examine
whether the addition of the website information makes any measurable impact on the
4 Terminology used to describe the operation of PHEVs is explained fully in the following sub- section:
Defining Terms.
10
vehicle performance as recorded by the on- board data systems. ( Most of the households
included in this report were not provided access to the website displaying their vehicle’s
data until halfway through their trial month.) Results from this first phase of interface and
instrumentation research are included in this report.
The second phase of instrumentation research builds on the first, but is not scheduled to
begin until summer 2009. In the second phase, a custom- made driver feedback display
will be included as part of the research design for a subset of the Project households. The
display device will allow the driver to choose from a variety of information to be
displayed. Evaluation will be based on additional survey and interview questions as well
as data recorded by the existing V2Green data systems and the new in- vehicle device.
Social Influence
Within this PHEV demonstration, a sub- group of 10 to 15 social networks ( each centered
on a household driving the PHEV- conversion) will be selected investigate how
interpersonal interactions influence the assessment and adoption of electric- drive
vehicles. Analysis of four networks has been completed to date and is discussed in this
report. Three research questions are addressed:
1. Do interpersonal interactions play a significant role in the assessment and
adoption of electric drive vehicles?
2. If so, how can we characterize the interpersonal interactions that influence
consumer perceptions of functional, symbolic, and pro- societal attributes?
3. Under what conditions might households adopt the pro- societal car?
To explore these research questions, this project maps, measures, and stimulates the
personal networks of selected households. A multi- method qualitative approach is
followed, combining semi- structured interviews, internet- based questionnaires, and a
social episode diary technique to track each social network. First, prior to receiving the
PHEV, the participating household is asked to map their social network and invite several
people from it to take part in the study. During each participant’s PHEV trial, information
11
is collected regarding their social discussions and interactions with network members—
seeking to characterize how social interactions influence perceptions, expectations, and
ultimately, purchase intention. Findings will help inform policymakers, researchers and
industry how new technologies with pro- societal attributes could enter the market.
Defining Terms
In this section we present the basic vocabulary that we will use throughout this report to
describe PHEVs. Some of this vocabulary is intended for readers of this report, i. e., it is
not the vocabulary we necessarily used when we spoke with our participants about
PHEVs. Describing where and how those two vocabularies diverge is one of the
developing outcomes of the overall research agenda of which this Project is a part.
A PHEV has both an electric motor and a heat engine— usually an internal combustion
engine ( ICE). 5 This flexibility also complicates vehicle designs and possible ways of
using energy from two different systems. Figure 1 shows two simple schematics of
possible PHEV architectures, i. e., the overall design of the PHEV system to supply power
from two different sources. A series architecture powers the vehicle only by an electric
motor using electricity from a battery. The battery is charged from an electrical outlet or
by the gasoline engine via a generator. A parallel architecture adds a direct connection
between the ICE and the wheels, adding the potential to power the vehicle by electricity
and gasoline simultaneously and by gasoline only. As examples of each architecture,
General Motors is working on a series architecture, e. g. the Chevy Volt and Toyota is
developing a PHEV with a parallel architecture, e. g. a plug- in version of the Prius.
Basic PHEV Design Concepts
Here we explain four fundamental PHEV concepts that will frame our questions with
participants throughout all phases of the PHEV research agenda and the Project in
particular. First, for any given architecture, a PHEV can operate in one of two modes:
charge sustaining ( CS) or charge depleting ( CD). Figure 2 ( adapted from Kromer and
5 As the ICEs in most conventional light- duty vehicles in the US are fueled with gasoline, we will refer to
gasoline and gasoline engines without precluding the possibility of other fuels.
12
Heywood, 2007, p. 31) illustrates these two modes. The vertical axis is the battery’s state
of charge ( SOC); the horizontal axis is the distance traveled. In practice, the maximum
SOC may be limited to less than 100 percent, and the minimum SOC higher to more than
0 percent, both to preserve battery life and improve safety. The difference between the
maximum and minimum SOC is known as the usable depth of discharge ( DOD), which
varies across battery and vehicle designs.
In the Figure 2 example, the battery is “ fully” charged ( from an electrical outlet) to 90
percent SOC. Once it starts driving, the PHEV is driven in charge- depleting ( CD)
mode— energy stored in the battery is used to power the vehicle, gradually depleting the
battery’s SOC. Once the battery is depleted to a minimum level, set at around 25 percent
in this example, the vehicle switches to charge- sustaining ( CS) mode. In CS mode the
SOC is sustained by relying primarily on the gasoline engine to drive the vehicle, only
using the battery and electric motor to increase the efficiency of the gasoline engine, as is
now done in an HEV. The vehicle remains in CS mode until the battery is plugged in to
the electric grid to recharge. The distance a fully charged PHEV can travel in CD mode
before switching to CS mode is one definition of CD range.
Figure 1: Basic PHEV Drivetrain Options— Series vs. Parallel Design
ENGINE
MOTOR
GENERATOR
ELECTRICAL
OUTLET
GASOLINE
MOTOR
GEN.
ELECTRICAL
OUTLET
GASOLINE
Battery
ENGINE
Battery
Series Parallel
13
Second, a PHEV can be designed for all- electric or blended operation in CD mode. A
PHEV designed for all- electric operation can be driven for the CD range using only
electricity from the battery, and the engine is not used at all. In contrast, a PHEV
designed for blended operation will use electricity and gasoline to power the vehicle
throughout the CD range— energy from the engine and the battery are “ blended” together
through the electro- mechanical drivetrain. Thus, a PHEV designed for all- electric driving
will require a battery capable of delivering more power than a PHEV designed for
blended driving because the battery ( and motor and power electronics) must be capable
of providing the full power of the vehicle, not just partial power.
Figure 2: Illustration of Typical PHEV Discharge Cycle ( 65% DOD)
Source: Adapted from Kromer and Heywood ( 2007, p31). Used with permission from authors.
Third, PHEV designs are commonly described according to CD range; the common
notation is PHEV- X, where X is distance in miles. For instance, a PHEV- 10 can be driven
10 miles in CD mode before switching to CS mode. However, this notation does not
Distance
Battery State of Charge ( SOC)
Charge Sustaining ( CS)
Charge Depleting
( CD) Range
Gasoline
Only
All Electric ( AE) or
Blended ( B)
14
distinguish whether a PHEV in CD mode is operating all- electrically or by blending, nor
does it specify the driving conditions that would allow CD mode for the stipulated
distance. Comparisons of PHEVs, even those sharing the same PHEV- X designation,
must reconcile assumptions regarding CD mode and driving behavior.
Kurani, Heffner, and Turrentine ( 2007) discuss how further confusion in PHEV notation
can result from two differing concepts of PHEV- X. First, Gondor and Simpson ( 2007)
argue that X should be defined as the equivalent number of miles of petroleum displaced
by electricity from the battery. This approach makes no distinction between all- electric
and blended operation; a fully charged PHEV- 10 could store and use enough electricity
to reduce gasoline use by the amount of gasoline required to travel 10 miles, but not
necessarily during 10 continuous miles of all- electric operation. On the other hand, the
California Air Resources Board ( CARB, 2003) defines X as the total miles that can be
driven before the gasoline engine turns on for the first time, also known as all- electric
range ( or zero- emissions range). By this definition, a fully charged PHEV- 10 could be
driven for the first 10 miles without using any gasoline. As of the writing of this report,
CARB is considering a proposal to allow PHEVs designed for blended operation to
receive credits under the zero emissions vehicle regulation ( CARB, 2008b).
Using the language developed in this section, the PHEV conversions used in this Project
could be described as blended PHEV- 30s, in which we adopt the definition of the
distance at which the vehicle switches from CD to CS operation as the definition of CD
range. We will return to this vehicle characterization in our conclusions, modifying it in
accordance with the on- road performance of our first 34 households.
15
2. PHEV DEMONSTRATION AND RESEARCH PLAN
The Project provides households with real- world experience with PHEVs prior to asking
them to evaluate such vehicles and offer their preferred PHEV designs.
Household PHEV Placements
PHEV- conversions are placed in households for periods of time that allow for the
household members to learn and adapt. Starting in late- August 2008, household
placements were initially scheduled for four weeks. After completing the research
process with over twenty households, we judged that four weeks was not long enough for
many of the households. In particular, some were still learning about recharging and its
effects on energy use and cost. Further, most households were still talking about the Prius
per se, leaving less time to discuss the added plug- in capability. 6
Starting in February 2009, households in the Project use the vehicles for six weeks. The
PHEV- conversion package allows for the conversion to be taken off- line, returning the
operation of the vehicle to that of a conventional Prius. 7 Therefore, the PHEV-conversions
are now delivered to the households with the conversion off- line. The
conversion is placed back on- line after two weeks. This allows the households to respond
to a ( more- or- less) conventional Prius and then move on to experience and evaluate a
particular PHEV. Further, the two- week pre- PHEV period allows us to establish a
baseline of driving performance based on data from the on- board data systems.
Participants are interviewed at the start of, during, and at the end of their PHEV trial to
make sure the vehicles are working properly and to explore with the household their use
of and response to the vehicle. Further, the households complete a screening
questionnaire ( used in recruiting participants) and the first and third parts of the
6 Of the households included in this report, only one was a pre- existing HEV owner. Additional HEV
owners are being included in the subsequent sample.
7 Because the conversion package adds weight, the Priuses in our demonstration— with the conversions off-line—
can be expected to return slightly worse fuel economy than unconverted Priuses.
16
questionnaire previously administered to representative samples of the US, California,
and the counties along the Interstate 80 corridor from the San Francisco Bay Area to
eastern suburbs of the Sacramento region. The last region was over- sampled in particular
to provide a comparative population for the households participating in the Project.
Sampling
Participants are recruited through an “ illustrative” sampling method ( Turrentine and
Kurani, 2007.) Such a sample does not attempt to be representative of a population;
rather, the purpose is to illuminate the behavior of specific groups. The sampling frame
for the Project is defined by 1) automotive insurance requirements, 2) geographic
location, 3) vehicle ownership, 4) driving, and 5) broad categories of household structure.
Participants are selected for the Project in a three- stage process. First, AAA Northern
California, Nevada & Utah issues an invitation to their automotive policyholders who 1)
meet minimum requirements regarding the amount of insurance they carry and their
driving records, and 2) live within the geographic region specified by researchers at UC
Davis. Presently that region is roughly defined as the area within about 30 to 45 minutes
driving time of Davis, CA. Second, volunteers from the recipients of the letter are
instructed to log- on to a website hosted on a UC Davis server, where they complete a
brief questionnaire which solicits more specifics of the potential participants vehicles,
home, travel, household, and contact information. Third, researchers review the
questionnaire responses and select households based on the goal to illustrate the
responses of different types of households.
An illustration of the interaction between Project management and research goals is the
geographic distribution of the participant households summarized in this report as shown
in Figure 3. To initially simplify the logistics of vehicle delivery, pickup, and household
interviews the first participants were selected from the city of Davis, CA. However, an
important research goal is to incorporate households in a variety of towns, cities, and land
use settings within these towns and cities. As can be seen in the figure, this goal is being
achieved and will be furthered as additional participants are selected during the remainder
of the Project.
17
Figure 3: Geographic distribution of PHEV Project participants ( n= 34)
The realized Project sample- to- date will be compared to the California and northern
California survey respondents after we describe the interviews and questionnaires from
which the comparative data are taken.
The Interviews and Questionnaires
Each household was interviewed three to five times: upon vehicle delivery, every two
weeks, and finally after the last week when the vehicle was retrieved. Interviews last
between one and two hours. Two researchers attend the first and last interviews. All
interviews are recorded; all but the first interview recordings are transcribed. The initial
interviews tend to be given over to formally enrolling the household in the study— which
must happen before the vehicle can be handed over and substantive interviewing can
begin. During this first interview, researchers primarily listen for the questions the
household has about the vehicle, offering answers that are as non- leading as possible. For
18
example, every household asks how often the vehicle should be plugged in. Our standard
response is that these cars can be driven without ever being plugged in, but that what we
are hoping to learn from the household is how often they plug- in and why.
The second and third interviews follow protocols, i. e., outlines of topic areas to be
covered with every household. Each topic area includes example prompts that are not
used in every household, but only as needed or appropriate to each household. An
example of the protocol is included in Appendix A.
In addition to the recruiting and screening questionnaire, each household in the Project
also completed a two- part online survey eliciting several types of data. The survey was
slightly modified from the instrument administered to over 2,200 U. S. respondents as
reported in Axsen and Kurani ( 2008). This previous study included over- samples of
California ( n= 851) and Northern California ( n= 216) in the region along Interstate- 80
from the San Francisco Bay Area to the eastern reaches of the Sacramento conurbation.
In this report, responses from these two samples are compared with the responses of
Project participants.
The primary survey instrument used in the PHEV Project is a set of two internet- based
questionnaires, each requiring 20 to 30 minutes to complete: 1) background information,
completed before the household drives the PHEV, and 2) plug- in hybrid electric vehicle
( PHEV) designs, completed after the household has driven the PHEV for several weeks.
Part One includes questions on vehicle ownership, knowledge of gasoline use and
spending, knowledge of electricity use and spending, awareness of electric- drive
vehicles, attitudes towards environmental and global issues, as well as household
structure, income, education and other demographic variables. Awareness of electric-drive
vehicles is assessed with questions eliciting the stated familiarity of respondents
with conventional gasoline, hybrid- electric, electric, and plug- in hybrid electric vehicles.
Respondents were then asked to demonstrate their understanding by choosing how each
vehicle type could be fueled: with gasoline, electricity through an electrical outlet, or
either. The implication of this exercise is not that consumers need to have a deep
technological understanding of electric- drive vehicles in order to buy them. However, we
19
feel that basic familiarity, i. e. whether or not the vehicle can be plugged in, may shape
participants experience with the PHEV- conversion during their trial period and ultimately
affect their PHEV design priorities. 8
The Part Two questionnaire focuses on PHEV design priorities elicited in two versions of
priority- evaluator games. Commonly, researchers will infer preferences for attributes of
alternative fuelled vehicles by presenting participants with a description of one or several
new technologies, followed with a set of hypothetical choice scenarios in which
respondents make several choices from sets of vehicles of different attributes ( see for
example Bunch et al., 1993; Ewing and Sarigollu, 2000; Potogolou and Kanaroglou,
2007). However, Heffner et al. ( 2007) demonstrate that more in- depth research, such as
household interviews, can reveal important information that choice experiments cannot.
To improve the quality of data gathered from Project participants, prior to the PHEV
design exercises, participants were provided a PHEV buyers’ guide describing basic
design options for PHEVs ( replicated in Appendix B). Respondents then completed two
PHEV design games ( replicated in Appendix C). The first was a PHEV Development
Priority game in which participants create PHEV designs over several iterations. Second
was a Purchase Design game, similar to the first, but the design possibilities were priced
in dollars and participants could reject buying a PHEV, retaining a conventional vehicle.
One key difference between the games utilized in this study and a stated choice exercise
is that the games are design exercises, not choice exercises. Rather than choose their
preferred vehicle design from a limited set of options ( typically repeated several times)
specified by the researchers, participants in the design games have a design envelope
available to them, and they construct their most favored design from within that envelope
subject to resource constraints. Kurani et al. ( 1996) discussed the basis for regarding
consumer evaluations, especially of novel products such as electric- drive vehicles, as
being constructed in the process of choosing ( or not choosing).
8 As asked of the prior national, statewide, and regional samples— who will not have experience with a
PHEV afforded to Project participants— the question was intended only to test whether basic familiarity
with electric- drive technologies affected PHEV design priorities.
20
Both games focused on four PHEV design attributes: ( 1) hours required for complete
recharge of a depleted battery, ( 2) gasoline use in CD mode, ( 3) miles of range in CD
mode, and ( 4) gasoline use in CS mode. In each game, a base PHEV design is offered
with capabilities easily achievable by current battery technology ( Axsen et al., 2008): a
PHEV that requires up to 8 hours to completely recharge, that can be driven for the first
10 miles in CD mode using blended operation that increases gasoline- only fuel economy
to 75 mpg, and that can improve fuel economy by 10 mpg when operating in CS mode
over an otherwise similar conventional internal combustion engine vehicle. 9 In both
games, participants were given opportunities to improve each attribute under different
resource conditions.
We chose these four attributes due to their importance in determining driving patterns as
well as reflecting technological capabilities. First, the time to recharge a depleted battery
in PHEVs more capable than the base design would take 6- 8 hours, but technology exists
to allow “ fast” charging in less than one hour— allowing for significantly different
recharge and driving patterns. Second, currently available PHEV conversions are
designed to provide blended CD mode. We specified upgrades to account for several
levels of gasoline- only fuel economy in blended operation: 75, 100, and 125 mpg. This
range includes the 100 mpg “ magic” number identified as important among some early
PHEV conversion owners ( Kurani et al., 2007). Because automakers such as General
Motors have announced plans to release PHEVs designed for all- electric operation, we
also include an all- electric CD upgrade option. Third, CD range depends on battery
energy capacity, and proposed designs typically range from 10 to 40 miles ( Pesaran et al.,
2007; Kromer and Heywood, 2007). The fourth category, fuel consumption in CS mode,
is comparable to the operation of today’s hybrid electric vehicles; the battery and electric
motor are used to improve the efficiency of the gasoline engine, not to use grid
9 Note that these PHEV design games are meant to represent a PHEV design space that is technologically
feasible and that allows respondents to tell us which ( and how much) of the four attributes are more or less
important, but not necessarily to produce precise vehicle specifications. For instance, the battery required
for our base PHEV design would likely require only 2 to 3 hours to fully recharge with a 110- volt circuit.
However, based on pre- testing, we chose to simplify attribute levels and ignore potential interactions to
create exercises that are more likely to be understood by our respondents.
21
electricity. Most hybridized drivetrains can increase fuel economy by 10 to 30 miles per
gallon ( mpg) relative to a similar size, weight, and performance vehicle.
The first exercise, the Development Priority game, presents participants with a
hypothetical scenario: an existing household vehicle is to be upgraded to a PHEV at no
cost. 10 The performance and appearance of their vehicle would remain the same, except
for the additional plug- in hybrid capabilities. Participants were presented with a base
PHEV model and given points they must allocate among potential upgrades. Over five
rounds of the Development Priority game, participants were provided progressively more
points ( Table 1). For the first three rounds of the game higher levels of upgrades of the
four attributes and more combinations of upgrades were also offered, expanding the
PHEV design envelope to observe participants’ allocation of resources. A screenshot of
the game, along with the language used for respondents, is portrayed in Figure 4.
Table 1: Upgrades for PHEV Development Priority game
Attribute
( base value)
Round One:
( 1 point)
Round Two:
( 2 points)
Rounds Three, Four
and Five:
( 4, 6 and 8 points)
Recharge time:
( 8 hours)
4 hours ( 1pt) 4 hours ( 1pt)
2 hours ( 2pt)
4 hours ( 1pt)
2 hours ( 2pt)
1 hour ( 3pt)
Charge depleting ( CD)
mpg and type:
( 75 mpg)
100 mpg ( 1pt) 100 mpg ( 1pt)
125 mpg ( 2pt)
100 mpg ( 1pt)
125 mpg ( 2pt)
All- electric ( 4pt)
CD range:
( 10 miles)
20 miles ( 1pt) 20 miles ( 1pt)
40 miles ( 2pt)
20 miles ( 1pt)
40 miles ( 2pt)
Charge sustaining ( CS)
mpg:
( Current mpg* + 10)
Current mpg
+ 20 ( 1pt)
Current mpg
+ 20 ( 1pt)
Current mpg
+ 30 ( 2pt)
Current mpg
+ 20 ( 1pt)
Current mpg
+ 30 ( 2pt)
10 Which household vehicle was to be “ upgraded” was determined in Part One of the survey as either the
vehicle that the household most recently purchased, or, the newer vehicle that is most frequently driven
( see the full survey in Appendix C).
22
Figure 4: Screenshot of Development Priority game ( Round Four)
The second exercise, the Purchase Design game, framed the PHEV design exercise in the
context of a future vehicle purchase. The questionnaire first elicited information about the
anticipated price, make, and model of the next new vehicle the respondent’s household
would likely buy. The respondent then completed two PHEV purchase exercises, each
comparing their anticipated conventional vehicle with a PHEV version of the same.
Participants were presented with a “ higher” price and “ lower” price PHEV purchase
conditions, where prices in both conditions also depended on whether the vehicle was a
car or truck ( Table 2). As in the Development Priority game, each exercise started with
the same base PHEV model, with additional upgrades available for added price. The
participant could choose either their anticipated conventional vehicle, the offered ( base)
PHEV, or to upgrade the PHEV. Figure 5 is a screenshot of this exercise.
23
Table 2: Price of upgrades for Purchase Design game
“ Higher” price “ Lower” price
Attributes Attribute level Car Truck Car Truck
Base premium
over conventional
$ 3,000 $ 4,000 $ 2,000 $ 3,000
Added premiums:
Recharge time 8 hours
4 hours
2 hours
1 hour
0
+$ 500
+$ 1,000
+$ 1,500
0
+$ 1,000
+$ 2,000
+$ 3,000
0
+$ 250
+$ 500
+$ 750
0
+$ 500
+$ 1,000
+$ 1,500
CD mpg and type
Blended
75 mpg
100 mpg
125 mpg
All- electric
0
+$ 1,000
+$ 2,000
+$ 4,000
0
+$ 2,000
+$ 4,000
+$ 8,000
0
+$ 500
+$ 1,000
+$ 2,000
0
+$ 1,000
+$ 2,000
+$ 4,000
CD range
10 miles
20 miles
40 miles
0
+$ 2,000
+$ 4,000
0
+$ 4,000
+$ 8,000
0
+$ 1,000
+$ 2,000
0
+$ 2,000
+$ 4,000
CS mpg Conventional mpg + 10
Conventional mpg + 20
Conventional mpg + 30
0
+$ 500
+$ 1,000
0
+$ 1,000
+$ 2,000
0
+$ 250
+$ 500
0
+$ 500
+$ 1,000
Because battery and drivetrain costs are uncertain, upgrade prices in Table 2 are
hypothetical. We are less concerned whether the prices we now present to participants
will be right in a future ( if and) when PHEVs are marketed, and more concerned with
how participants respond in the PHEV design space within different price contexts. Still,
the price contexts we present are not wholly imaginary. Overall, prices are based on short
term ( high price) and long term ( low price) estimates from previous studies: Markel
( 2006) estimates incremental costs for PHEVs with all- electric capabilities ( 7 to 19 kWh)
at $ 6,000 to $ 22,000, while Kalhammer et al. ( 2007) provide cost estimates for PHEVs
with slightly lower capacity batteries ( 4 to 14 kWh) in the range of $ 2,000 to $ 8,000.
Price premiums for PHEV designs in our survey ranged from $ 3,000 to $ 13,500 for cars
in the “ high” price condition, and from $ 2,000 to $ 7,250 in the “ low” price condition. For
trucks, base model PHEV prices are increased and upgrades doubled based on Duvall et
al.’ s ( 2002) estimates of a full size SUV PHEV requiring 75 percent more energy
capacity and 190 percent more battery power to achieve the same CD performance as a
compact car PHEV.
24
Figure 5: Screenshot of Purchase Design game (“ high” price, vehicle
model customized for respondent)
Who are the Project Participants?
To explore whether findings from the Project can be generalized to other people, we
describe briefly who the Project respondents are and how they compare to other larger
samples. These include the California and northern California over- samples we surveyed
during our nationally representative survey of new car buying households. Other
comparisons are made to the 2001 Nationwide Household Travel Survey, the 2005- 07
American Community Survey, and the 2000 United States Census.
25
Descriptions of the samples on the following attributes are presented in Table 3:
household hybrid vehicle ownership, respondents’ gender, education, age, household
income, and housing type. One important difference between the Project participants and
all other samples is that Project participants are chosen, in part, because they have a place
at home to recharge the PHEV— we judged it to be of little value to give a vehicle to a
household who could not routinely and easily recharge the vehicle, if they chose to. This
choice on our part will introduce some differences in income and housing type as seen in
Table 3. Finally, the description of the Project households is highly provisional and will
change by design over the remainder of the Project.
Our sample contains about the same proportion of HEV owners as do our survey over-samples
for northern California and California— but still, this is one HEV owner ( to
date). Though we cannot report hybrid vehicle ownership rates for the ACS or Census
samples, it seems clear that all our survey and Project samples contain a higher
proportion of hybrid owners than exist in the general population. Still, the over-representation
is not so large as to skew overall responses. We expect that the percentage
of hybrid owners in the Project sample will ultimately be higher than it is now.
The gender balance of the present Project participants represents that of the general
population and California over- sample; the northern California over- sample is skewed
toward male respondents. The Project participants are skewed toward people with
graduate educations— even compared to our survey over- samples, which are skewed
toward higher education compared to the general population samples. Respondents in all
three of our samples are much more likely to be between the ages of 35 and 54 than the
general population; the skew toward this age group is even stronger in the present Project
sample than in the survey over- samples. As with education and age, the present sample of
Project participants amplifies the distinctions from the general population of the survey
over- samples: the over- samples of new car buyers in California and northern California
are more likely to have higher household incomes than the general population and the
Project participants are even more likely to have higher incomes. As noted above, by
design ( or rather, because of known correlations between housing type and ability to
recharge at home) our survey respondents are far more like to live in detached homes.
26
Table 3: Comparing Project participants, survey respondents, and the general population
Target AAA members New vehicle buyers General population
Year 2008- 9 2007 2007 2001 2005- 7 2000
Data source
PHEV Demo
PHEV Survey
( Nor. Cal.) a
PHEV Survey
( Cal.) a
NHTSb
( Cal.)
ACS f
( Cal.)
Census g
( Cal.)
Sample size 34 216 851 389
Hybrid owner? Yes 11.8% 8.9% 10.6% - - -
Genderc Male 49.2% 59.7% 48.5% 44.5% 50.0% 49.7%
Female 50.8% 40.3% 51.5% 55.5% 50.0% 50.3%
Educationd High school or lower 9.1% 2.6% 8.8% 22.1% 43.0% 43.3%
Some college 21.2% 34.9% 33.9% 22.1% 20.4% 22.9%
College degree 30.3% 32.8% 39.5% 39.9% 26.3% 24.2%
Graduate degree 39.4% 29.7% 17.8% 15.9% 10.4% 9.5%
Agec 15 to 24 3.2% 4.6% 3.3% 6.5% 19.0% 18.3%
25 to 34 8.1% 21.1% 20.5% 18.0% 18.3% 19.8%
35 to 44 25.8% 27.3% 29.0% 23.5% 19.3% 21.6%
45 to 54 27.4% 29.4% 23.7% 24.8% 17.6% 16.5%
55 to 64 29.0% 10.8% 15.1% 13.3% 12.1% 9.9%
> 64 6.5% 6.7% 8.3% 13.8% 13.8% 13.8%
Household < 30 k 3.1% 1.8% 2.0% 6.3% 25.3% 31.2%
income 30 k to 60 k 15.6% 11.9% 17.6% 23.4% 25.8% 29.5%
> 60k to 100k 15.6% 35.1% 27.7% 32.3% 23.0% 22.1%
> 100k 65.6% 51.2% 52.7% 38.0% 25.8% 17.3%
Mean incomee $ 117,734 $ 106,949 $ 104,814 $ 84,416 $ 73,944 $ 61,441
Ratio of mean incomes
( new vehicle buyer/ gen. pop.) 1.59 1.45 1.42 1.37
Housing typed Detached house 94.1% 71.3% 68.1% 79.4% 58.0%
Attached house 5.9% 10.3% 11.9% 4.4% 7.0%
Apartment 0% 17.9% 16.7% 13.6% 30.7%
Mobile home 0% 0.5% 3.4% 2.6% 4.2%
a U. S. weights provided by Harris Interactive.
b NHTS sample limited to responding California households that had purchased a vehicle of model year 2001 or 2002.
c For PHEV Project: data reported for all participants; for PHEV survey: data only reported for responding member of household.
d For PHEV Project and PHEV survey: data only reported for responding member of household.
e Mean approximated from the product of middle values assigned to each income category and the proportion of the sample in that category.
f 2005- 2007 American Community Survey 3- year estimates, California.
g 2000 Census by the U. S. Census Bureau.
27
Gasoline Prices Faced by Survey Respondents and Project Participants
One question we are repeatedly asked regarding the national study is, “ When was it done
in comparison to the run- up of gasoline prices to past $ 4.00 per gallon during the summer
of 2008?” The answer is that the national survey was conducted in December 2007 and
precedes the rise of gasoline prices past $ 4.00 per gallon by several months. The average
price last paid for gasoline by the California and northern California samples were both
about $ 3.40 per gallon as shown by the horizontal lines in Figure 6.
Figure 6: Comparing gasoline prices from survey respondents ( lines) and
Project participants ( diamonds)
$-
$ 0.50
$ 1.00
$ 1.50
$ 2.00
$ 2.50
$ 3.00
$ 3.50
$ 4.00
$ 4.50
$ 5.00
2- Aug- 08 1- Sep- 08 1- Oct- 08 31- Oct- 08 30- Nov- 08 30- Dec- 08 29- Jan- 09 28- Feb- 09
Date
$/ Gallon
Survey Average, December 2007 ( All California)
Survey Average, December 2007 ( North California)
In contrast, the first Project participants were paying well in excess of $ 4.00 per gallon
for gasoline in August 2008. But these are a small minority of Project participants, as
prices quickly declined through September and October 2008 to, and then below, the
average of the price faced by the national survey respondents. Still, whether they faced
higher gasoline prices during their PHEV trial period or whether they simply recall such
higher prices from last summer, we expect that our Project participants may be more
sensitive to the uncertainty of gasoline prices than the national survey respondents were
at that time. This may make Project participants less like our survey respondents, but
28
makes them more like their peers, i. e., all car- buying households, who have now lived
through this same price history.
Motivations and Knowledge regarding Electric- drive
The invitation sent by AAA Northern California, Nevada & Utah did not emphasize
motivations to volunteer; still, one might speculate that the households volunteering for a
PHEV demonstration project have stronger motivations and knowledge regarding
electric- drive vehicles than households in general. Responses to three questions regarding
motivations are summarized in Figure 7: global warming, air pollution, and energy
( in) dependence. The Project sample contains a slightly higher percentage of people who
state that each of these three issues is “ a serious problem, and immediate action is
necessary” than in the California and northern California survey samples. Still the
differences are small. We judge the differences to be unlikely to make a substantive
difference in any conclusions we may draw between the samples on their PHEV designs.
On the issue of knowledge regarding electric- drive vehicles, a question in the first part of
the questionnaire completed by both the survey sample and Project participants asked
respondents to rate their familiarity with conventional, electric, hybrid- electric, and plug-in
hybrid vehicles. This was followed up by a question asking how each of these four
types of vehicles are fueled and/ or recharged. Responses to this second question are
summarized in Figure 8. In general, there is little to distinguish the knowledge of electric
drive vehicles among the Project participants from the survey respondents— except on the
specific issue of plug- in hybrids. Across all samples, very high percentages of
respondents know that a plug- in hybrid can be both fueled and plugged- in; the highest
percentage is among our Project participants. There are a few opportunities for
“ information leaks” to the project households about PHEVs— the recruiting phone call
and the information provided to households when the PHEV is first delivered.
29
Figure 7: Comparing environmental beliefs among survey respondents
(“ CA” and “ NCA”) and Project participants (“ Demo”)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
CA
NCA
Demo
CA
NCA
Demo
CA
NCA
Demo
% Choosing Statement
It is a serious problem, and
immediate action is necessary.
It could be a serious problem,
and we should take some
action now.
It is not a problem and does not
require any action.
More research is needed
before action is taken.
Global warming
( climate change)
Air pollution The dependency
of the U. S. on
foreign oil
Figure 8: Comparing electric- drive knowledge among survey respondents
( CA and NCA) and Project participants (“ Demo”): “ From what you
understand of these vehicle technologies, which can use fuel, and which
can be plugged in?”
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
CA
NCA
Demo
CA
NCA
Demo
CA
NCA
Demo
CA
NCA
Demo
% Choosing Statement
Only with
gasoline
Only by plugging
in
Either
Conventional
vehicle ( CV)
Electric
vehicle ( EV)
Hybrid- electric
vehicle ( HEV)
Plug- in hybrid
vehicle ( PHEV)
30
3A. PROJECT RESULTS: PHEV DESIGNS
All participants in the Project and in the prior survey research created PHEV designs. We
use these designs as measures of what is interesting and valuable to respondents about
PHEVs. In addition to our inherent interest in the PHEV designs created by the Project
participants, we are interested in whether and how the Project participants’ designs differ
from those created by the prior survey respondents.
Whose PHEVs? Plausible early markets
This section compares the PHEV designs elicited from the 34 households who completed
their Project participation between August 2008 and April 2009 with those elicited from
respondents in the California ( CA) and northern California ( NCA) over- samples of the
national survey in December 2007. The PHEV design games were described in the
previous section, and reproduced in Appendices B and C. In this section, PHEV design
priorities are reported only for respondents classified as plausible early market PHEV
buyers by satisfying two requirements: 1) they demonstrate access to sufficient recharge
infrastructure, defined here as home access to an electrical outlet for their vehicle, and 2)
interest in PHEVs as indicated by a reported purchase intention in the “ higher” price
condition of the Purchase Design game. Based on these conditions, Axsen and Kurani
( 2008) described 33.5 percent of responding U. S. new car buyers as plausible early
market respondents. In the California over- sample, 45.8 percent of respondents park their
vehicle within 25 feet of an electrical outlet at home, and of these, 73.5 percent indicate
PHEV purchase intention in the “ higher” price scenario, and thus 33.7 percent of the total
California sample are classified as the plausible early market respondents ( n= 286). In the
northern California over- sample, 45.6 percent have home recharge access, 71.3 percent of
which indicate a PHEV purchase intention, and thus 32.5 percent of the total sample is
classified as plausible early market respondents ( n= 63). 11 Among the PHEV Project
11 Because of the small samples for the households who completed their Project participation by April 2009
and for the plausible early market respondents in northern California, the comparisons made here are
descriptive and exploratory rather than ( necessarily) representative.
31
participants, all have access to home recharging because it is a requirement for
participation. Among these 34 households, 30 ( 88 percent) indicate a PHEV purchase
intention in the higher price scenario and thus these 88 percent are included as the
plausible early market Project participants. Clearly nothing about the likeliness to design
a PHEV as their plausible next new vehicle purchase distinguishes the California and
Northern California survey samples from the national sample; equally clearly, Project
participants are more likely to design their next new car as a PHEV. Given they are more
likely to design a PHEV, are our Project households designing different PHEVs than did
our survey respondents?
What PHEVs do they Design?
The PHEV Purchase Design game first asks households to select a vehicle they were
most likely to buy next. Figure 9 compares these base vehicles selected by survey
respondents with those selected Project participants. Notably, 67 percent of Project
participants selected some variety of HEV and 40 percent selected a Toyota Prius. These
percentages are 2 to 3.5 times higher than those of the CA and NCA samples, indicating a
much more frequent interest in hybrid vehicles among Project participants ( after their
PHEV trial) than was elicited from a broader samples of CA and NCA car buyers ( who
lacked direct experience with a PHEV). This difference may not be due to a
predisposition and/ or self- selection of Project participants. Recall from their previous
description that Project participants: are not substantially more likely to own a hybrid, do
not possess more knowledge about electric drive vehicles, and do not have more concern
for environmental or global issues— at least not to such a degree as to warrant a 2 to 3.5
fold increase in hybrid interest in these design games. One explanation supported by the
household interviews that because Project participants completed the PHEV Purchase
Design game after driving the PHEV- conversion for several weeks, participants had
become more interested in hybrids in general, and in the Toyota Prius in particular.
32
Figure 9: Comparing base vehicles chosen for PHEV Purchase Design
Game ( plausible early market only: CA, n= 286; NCA, n= 63; Project, n= 30)
0%
20%
40%
60%
80%
100%
CA NCA Demo
Sample
Base Vehicle for Future
Purchase (% of Sample)
Conventional
Car
Conventional
Truck
Toyota Prius
Other HEV
Focusing on the interests of these plausible early market Project participants, results of
the two PHEV design games are summarized in Figure 10. In Round One of the
Development Priority game, respondents were given one point to allocate towards one
upgrade to the base PHEV model. As described previously, four upgrades were available:
recharge time ( from 8 to 4 hours), gasoline- fuel economy during CD mode ( from 75 to
100 mpg), CD range ( from 10 to 20 miles), or CS gasoline- fuel economy ( from 10 to 20
mpg over the conventional version of the vehicle). Improving the CD range was the most
frequently chosen upgrade ( 50.0 percent), while improving CS fuel economy was a close
second place ( 39.3 percent). 12 The general ranking of attribute upgrades in Round One
continues through later rounds: a higher percentage of potential early market respondents
designed PHEVs with CD range upgrades and CS fuel economy upgrades, as well as CD
type in later rounds, and few respondents designed PHEVs with faster recharge times.
12 Although the percentages add up to 100 across the columns in Round One, they do not in further Rounds
because respondents have enough points to choose multiple upgrades.
33
Figure 10: Upgrades selected in PHEV design games by Project
participants ( plausible early market Project participants only, n= 28)
0%
20%
40%
60%
80%
100%
Recharge
CD Type
CD Range
CS MPG
Recharge
CD Type
CD Range
CS MPG
Recharge
CD Type
CD Range
CS MPG
Recharge
CD Type
CD Range
CS MPG
Recharge
CD Type
CD Range
CS MPG
Recharge
CD Type
CD Range
CS MPG
Base Model
Recharge
CD Type
CD Range
CS MPG
Base Model
% Choosing Upgrade
Base Model
3rd Level Upgrade
2nd Level Upgrade
1st Level Upgrade
Game 1: Development Priority ( Points) Game 2: Purchase Design ($)
Round 1
( 1pt)
Round 2
( 2pt)
Round 3
( 4pt)
Round 4
( 6pt)
Round 5
( 8pt)
“ High”
Price
“ Low”
Price
All- electric operation ( in CD mode) was first offered to respondents in Round Three of
the Development Priority game; only one of the 28 households ( 3.6 percent) incorporated
this upgrade into their PHEV, which came at the expense of any other upgrades available
in prior rounds. 13 In Round Four, the number of plausible early market Project
participants designing a PHEV with all- electric operation rose to six ( 21.4 percent).
Figure 11 portrays the 23 different possible PHEV designs possible in Round Four. This
is the first round in which the design envelope allows a PHEV with 40 miles of all-electric
range— a vehicle performance ( at least as measured by CD mode and range)
similar to GM’s Volt concept. Only three of plausible early market Project participants
( 10.7 percent) created this specific design. Overall, all- electric operation was not a
chosen frequently when points were relatively scarce and alternative design possibilities
were available, i. e. in Rounds Three and Four of the Design Priority game. PHEV
13 Although 30 households were previously identified earlier as the plausible early market PHEV demo
participants, data from the development priority game ( game 1) are only reported for 28 households due to
missing data ( Figure 10, Figure 11, and Figure 13).
34
performance priorities varied substantially; no single PHEV design emerged as a majority
favorite. Still, the Project sample to date is the most heavily skewed toward a single
design, i. e., 8 hours recharging, 125mpg for 40 miles in CD operation, and + 30 mpg in
CS operation ( compare to Figures 14 and 15).
Figure 11: Distribution of selected PHEV designs in Round Four of
Development game ( plausible early market only: Project, n= 28)
0% 10% 20% 30% 40% 50%
2 Hours_ 75 MPG_ 40 Miles_+ 30 MPG
1 Hours_ 75 MPG_ 40 Miles_+ 20 MPG
1 Hours_ 75 MPG_ 20 Miles_+ 30 MPG
4 Hours_ 100 MPG_ 40 Miles_+ 30 MPG
2 Hours_ 100 MPG_ 40 Miles_+ 20 MPG
2 Hours_ 100 MPG_ 20 Miles_+ 30 MPG
1 Hours_ 100 MPG_ 40 Miles_+ 10 MPG
1 Hours_ 100 MPG_ 20 Miles_+ 20 MPG
1 Hours_ 100 MPG_ 10 Miles_+ 30 MPG
8 Hours_ 125 MPG_ 40 Miles_+ 30 MPG
4 Hours_ 125 MPG_ 40 Miles_+ 20 MPG
4 Hours_ 125 MPG_ 20 Miles_+ 30 MPG
2 Hours_ 125 MPG_ 40 Miles_+ 10 MPG
2 Hours_ 125 MPG_ 20 Miles_+ 20 MPG
2 Hours_ 125 MPG_ 10 Miles_+ 30 MPG
1 Hours_ 125 MPG_ 20 Miles_+ 10 MPG
1 Hours_ 125 MPG_ 10 Miles_+ 20 MPG
8 Hours_ Electric Only_ 20 Miles_+ 20 MPG
8 Hours_ Electric Only_ 10 Miles_+ 30 MPG
4 Hours_ Electric Only_ 20 Miles_+ 10 MPG
4 Hours_ Electric Only_ 10 Miles_+ 20 MPG
2 Hours_ Electric Only_ 10 Miles_+ 10 MPG
8 Hours_ Electric Only_ 40 Miles_+ 10 MPG
As previously noted, results of the Purchase Design game suggest that the majority of
Project participants would value PHEV capabilities in their next vehicle. Figure 10 also
depicts the proportion of upgrades chosen in the price conditions for this second version
of a PHEV design game. Seven of plausible early market Project participants ( 25
percent) chose the base PHEV models with no upgrade in both price conditions. Among
those who created higher cost designs, overall patterns of these designs are similar to
those created in the Development Priority game; CS fuel economy upgrades were chosen
more often than other upgrades, and there is no evidence of the strong interest in all-
75 mpg
100 mpg
125 mpg
Electric
O l
PHEV Design Combination:
( Recharge_ CD Type_ CD Range_ CS MPG)
% of Respondents Choosing Design
" Volt" Design:
Recharge = 8 hours
CD Type = Electric Only
CD Range = 40 miles
CS mpg = + 10 mpg
35
electric operation observed among some pioneer PHEV conversion drivers ( Kurani et al.,
2007). All- electric upgrades were chosen by two households ( seven percent) and four
households ( 13 percent) in the higher and lower price conditions, respectively.
Figure 12 depicts the proportion of CD type and CD range designs selected by Project
participants. Note that 11 households ( 37 percent) designed a PHEV capable of 75 mpg
for the first 10 miles, and that 24 households ( 86 percent) designed a blended CD design
( as opposed to all- electric) with a range of 20 miles or less. Such designs have far lower
battery requirements than the all- electric, longer- range designs assumed by various
battery experts ( Axsen et al., 2008).
Figure 13 compares Round 4 of the Development Priority game results from plausible
early market Project participants with those respondents from the CA and NCA samples.
Results are fairly similar across samples, though Project participants selected recharge
upgrades less frequently, and selected 100 CD mpg and + 30 CS mpg more frequently.
Figures 14 and 15 show the distribution of PHEV designs in Round Four in the CA and
NCA samples, respectively for comparison to Figure 10.
All figures indicate a wide variety of PHEV design interests among households, without
any particular draw to the all- electric 40- mile “ Volt” concept. Figure 16 compares the
same samples in terms of the higher price scenario of the PHEV Purchase Design game,
where a substantially higher proportion of Project participants selected some level of CD
type and range upgrades. Several differences among samples could contribute to this
trend; Project participants have: higher household income ( as portrayed in Table 3) and
more experience with PHEV driving ( having actually driven a PHEV for several weeks),
as well as other potential differences in driving patterns, commute patterns or other
factors that were not measured in all three samples.
36
Figure 12: Distribution of selected PHEV designs in high price scenario of
Purchase Design Game ( plausible early market Project participants only,
n= 30)
     '   
       	  
    	  
      	 
75 MPG
100 MPG
125 MPG
All- Electric
37% designed PHEV
with 10 mile range of 75 mpg
Figure 13: Comparing upgrades selected in Round 4 of Development
Priority game, ( plausible early market only: CA, n= 286; NCA, n= 63; Project,
n= 28
0%
20%
40%
60%
80%
100%
CA
NCA
Demo
CA
NCA
Demo
CA
NCA
Demo
CA
NCA
Demo
% Choosing Upgrade
3rd Level Upgrade
2nd Level Upgrade
1st Level Upgrade
Recharge
( 4h, 2h, 1h)
CD MPG
( 100, 125, AE)
CD Range
( 20, 40 miles))
CS MPG
(+ 20, + 30)
37
Figure 14: California Distribution of selected PHEV designs in Round Four
of Development game ( plausible early market only: CA, n= 286)
0% 10% 20% 30% 40% 50%
2 Hours_ 75 MPG_ 40 Miles_+ 30 MPG
1 Hours_ 75 MPG_ 40 Miles_+ 20 MPG
1 Hours_ 75 MPG_ 20 Miles_+ 30 MPG
4 Hours_ 100 MPG_ 40 Miles_+ 30 MPG
2 Hours_ 100 MPG_ 40 Miles_+ 20 MPG
2 Hours_ 100 MPG_ 20 Miles_+ 30 MPG
1 Hours_ 100 MPG_ 40 Miles_+ 10 MPG
1 Hours_ 100 MPG_ 20 Miles_+ 20 MPG
1 Hours_ 100 MPG_ 10 Miles_+ 30 MPG
8 Hours_ 125 MPG_ 40 Miles_+ 30 MPG
4 Hours_ 125 MPG_ 40 Miles_+ 20 MPG
4 Hours_ 125 MPG_ 20 Miles_+ 30 MPG
2 Hours_ 125 MPG_ 40 Miles_+ 10 MPG
2 Hours_ 125 MPG_ 20 Miles_+ 20 MPG
2 Hours_ 125 MPG_ 10 Miles_+ 30 MPG
1 Hours_ 125 MPG_ 20 Miles_+ 10 MPG
1 Hours_ 125 MPG_ 10 Miles_+ 20 MPG
8 Hours_ Electric Only_ 20 Miles_+ 20 MPG
8 Hours_ Electric Only_ 10 Miles_+ 30 MPG
4 Hours_ Electric Only_ 20 Miles_+ 10 MPG
4 Hours_ Electric Only_ 10 Miles_+ 20 MPG
2 Hours_ Electric Only_ 10 Miles_+ 10 MPG
8 Hours_ Electric Only_ 40 Miles_+ 10 MPG
% of Respondents Choosing Design
PHEV Design Combination:
( Recharge_ CD Type_ CD Range_ CS MPG)
" Volt" Design
75 mpg
100 mpg
125 mpg
Electric
Only
38
Figure 15: Northern California Distribution of selected PHEV designs in
Round Four of Development game ( plausible early market only: NCA, n= 63)
0% 10% 20% 30% 40% 50%
2 Hours_ 75 MPG_ 40 Miles_+ 30 MPG
1 Hours_ 75 MPG_ 40 Miles_+ 20 MPG
1 Hours_ 75 MPG_ 20 Miles_+ 30 MPG
4 Hours_ 100 MPG_ 40 Miles_+ 30 MPG
2 Hours_ 100 MPG_ 40 Miles_+ 20 MPG
2 Hours_ 100 MPG_ 20 Miles_+ 30 MPG
1 Hours_ 100 MPG_ 40 Miles_+ 10 MPG
1 Hours_ 100 MPG_ 20 Miles_+ 20 MPG
1 Hours_ 100 MPG_ 10 Miles_+ 30 MPG
8 Hours_ 125 MPG_ 40 Miles_+ 30 MPG
4 Hours_ 125 MPG_ 40 Miles_+ 20 MPG
4 Hours_ 125 MPG_ 20 Miles_+ 30 MPG
2 Hours_ 125 MPG_ 40 Miles_+ 10 MPG
2 Hours_ 125 MPG_ 20 Miles_+ 20 MPG
2 Hours_ 125 MPG_ 10 Miles_+ 30 MPG
1 Hours_ 125 MPG_ 20 Miles_+ 10 MPG
1 Hours_ 125 MPG_ 10 Miles_+ 20 MPG
8 Hours_ Electric Only_ 20 Miles_+ 20 MPG
8 Hours_ Electric Only_ 10 Miles_+ 30 MPG
4 Hours_ Electric Only_ 20 Miles_+ 10 MPG
4 Hours_ Electric Only_ 10 Miles_+ 20 MPG
2 Hours_ Electric Only_ 10 Miles_+ 10 MPG
8 Hours_ Electric Only_ 40 Miles_+ 10 MPG
Figure 16: Three- Sample Comparison of upgrades selected in higher price
scenario of Purchase Design game ( plausible early market only: CA, n= 286;
NCA, n= 63; Project, n= 30)
0%
20%
40%
60%
80%
100%
CA
NCA
Demo
CA
NCA
Demo
CA
NCA
Demo
CA
NCA
Demo
CA
NCA
Demo
% Choosing Upgrade
Base Model Only
3rd Level Upgrade
2nd Level Upgrade
1st Level Upgrade
Recharge
( 4h, 2h, 1h)
CD Type
( 100, 125, AE)
CD Range
( 20, 40 miles))
CS MPG
(+ 20, + 30)
No Upgrades
75 mpg
100 mpg
125 mpg
Electric
Only
% of Respondents Choosing Design
" Volt" Design
PHEV Design Combination:
( Recharge_ CD Type_ CD Range_ CS MPG)
39
PHEV Design Conclusions
In summary, the variety of PHEV designs created by survey respondents and Project
participants suggests there is still opportunity for automakers to explore and develop
different PHEV designs. We found little evidence of inherent demand for all- electric
operation in CD mode, even among Project participants who had experience driving a
( CD blended- operation) PHEV for a month— though our Project cannot presently exclude
the possibility of participants anchoring on what we have now made familiar to them, i. e.,
blended rather than all- electric CD operation. An even smaller subset was interested in
creating a vehicle with performance attributes combining 40 miles of CD range with all-electric
CD operation. These patterns contrast with the findings of Kurani et al.’ s ( 2007)
interviews with “ pioneer” PHEV conversion drivers who exhibited strong interest in
maximizing CD range and moving toward all- electric operation— effectively to approach
the capabilities of pure electric vehicles. This difference suggests that while all- electric
CD operation may be particularly attractive to a small subset of consumers, including
those who already have extensive knowledge and experience with electric vehicles, at
this point in time most households who buy new vehicles are more interested in high fuel
economy, even after completing a multi- week trial with one PHEV incarnation.
Participation in the Project appears to have decreased the importance of improvements in
recharging rates compared to prior survey respondents, but keep in mind Project
participants are selected in part because they are able to recharge at home. Project
participants are somewhat more likely to design a PHEV for their next new vehicle—
rather than revert to a conventional vehicle— than are the survey respondents. Project
participants are also more likely to choose a HEV as their base new vehicle from which
to consider the design of a PHEV.
The wide variety of PHEV designs created by survey respondents and Project participants
support the notion of a “ blank slate” early PHEV market, where early buyers may have
little in the way of PHEV performance expectations. That is, not only is there room for a
variety of technical pathways, but also there is room for multiple meanings of PHEVs.
Desired PHEV designs and capabilities may be subject to change. Project participants
40
and survey respondents had little pre- existing understanding of PHEVs and the responses
we elicited are sensitive to the PHEV information and experience we did provide. As
information about PHEV technology, costs, benefits, and meanings are transmitted
throughout the population, interest in particular PHEV attributes and performances could
shift too. For example, all- electric CD operation could become more meaningful to, and
valued by, car buyers as they gain experience with all- electric driving and as they
participate in the process of identifying just what all- electric operation means to people.
Our respondents PHEV designs suggest the possibility of a trajectory over time of PHEV
and electric- drive market development. Our respondents are designing PHEVs that are far
more technologically and financially feasible than “ experts” assume. In particular, most
of those designs provide some all- electric driving, as even PHEVs that use blended
operation in CD mode afford some all- electric driving. If we start with these less
aggressively electric designs, then over subsequent market and vehicle generations, the
electric capabilities of PHEVs can be increased as costs come down— due to learning by
doing, technology development, and improved designs— at the same time that more
consumers have learned to value increased electric- drive capabilities.
41
3B. PROJECT RESULTS: RECHARGING
PHEVs provide some degree of fuel flexibility to consumers, giving them the option of
using gasoline and grid- generated electricity. Given that the effects of PHEVs on energy
use, the environment, and the electricity grid depend on driving and recharging
behaviors, there is particular interest in how often PHEV owners will recharge a vehicle
that does not have to be recharged and when PHEV owners will recharge their vehicles.
The “ fuel” mix and the carbon content of the electricity used to recharge electric- drive
vehicles will vary according to how often, when, and where vehicles are recharged.
Furthermore, in examining future “ smart grid” scenarios in which vehicles may act as
mobile power sources ( or sinks), it is important to begin to replace analysts’ assumptions
with measures of PHEV owners’ driving and recharging behaviors. From the 34
households- to- date, we have obtained detailed information about their driving and
recharging behaviors. In this section, we summarize how participants, with minimum
input from researchers, acted with regards to the frequency, time of day, and location of
recharging.
Drivers in this Project have the option of recharging a vehicle to decrease gasoline use
and increase electricity consumption for the duration of the supplemental battery’s
charge. Recall, the PHEV- conversions used in this Project provide blended operation in
CD mode: the cars are still subject to the underlying HEV hardware and software. During
CD mode these PHEV- conversions will blend in more electricity than does a
conventional Prius ( which operates only in CS operation). Like a conventional Prius, it is
practically difficult to achieve sustained all- electric driving in real- world conditions.
All figures presented in this section are based on the last week of each household’s trial
with the PHEV conversion. This provides a common period over which we can compare
the same number of days and days of the week from each household. Also, the last week
represents the highest degree of uniformity of understanding about recharging behavior
across the households. Finally, since we judge that the households had developed their
recharging habits by this last week ( or had developed their habits as much as they were
going to in the course of their PHEV trial), we view their final week with the PHEV as
42
most representative of how these vehicles would be recharged by the households in the
future. This judgment is generally confirmed by the household interviews.
Perhaps more than any other information presented in this report, readers are cautioned
against generalizing our observations here to all PHEVs and users. Daily life provides
rhythms and routines that might shape behavior, for example the PHEV recharging
frequency discussed next. Still, we believe that PHEV recharging behavior may also be
shaped by the relationship between personal and household travel on the one hand and
PHEV designs, especially all- electric vs. blended CD operation and CD range, on the
other. For example, while the weight of evidence gathered so far in this Project suggests
that households owning PHEVs will, on average, plug- in the PHEV more than once per
day in an unconstrained world ( as will be detailed next), we are not yet prepared to
dismiss the argument that if these households had been given PHEVs with a different CD
range, the frequency of households plugging in different PHEVs to the electric grid may
be different than we observed. 14
How often do People Plug- in their PHEV- conversions?
The frequency with which people plug- in PHEVs to the electrical grid is perhaps the
central daily behavior affecting the energy, environmental, and social benefits of PHEVs.
Other important behaviors include the purchase of a PHEV whose CD range allows the
household to accomplish the greatest proportion of miles driven in CD mode ( constrained
by the expense of buying too much CD driving range) before their next recharge
opportunity and driving behaviors affecting overall efficiency, notably accelerations, top
speeds, and routes. The context for interpreting the PHEV recharging behavior observed
to- date in this Project is as follows. First, the only participants in this Project are people
who can recharge a PHEV at their home. Second, as most households lacked a sense of
the etiquette that would shape recharging at away- from- home locations, less away- from-
14 We use the phrase “ plugging- in” to refer to all acts of connecting the vehicle to the electrical grid,
regardless of the final state of charge of the battery when the vehicle is unplugged. We do this to create a
more general category that contains both “ recharging,” with its connotations of returning the battery to 100
percent SOC, and partial recharging, in which the vehicle is unplugged and driven before the battery
reaches 100 percent SOC.
43
home recharging was observed than may otherwise occur in a world where the rules and
conventions are known. Households who noticed “ EV” parking and recharging spaces
often asked us whether they could park and charge their PHEVs in such spaces. The few
bolder individual who tried discovered that such spaces presently lack 110- volt outlets
suitable for the PHEVs they were driving. Many people said they were uncertain of the
propriety of asking friends, acquaintances, and business- owners to recharge. ( See the
discussion of recharging etiquette in the later section on narratives.) Third, no household
was provided with time- of- day electricity tariffs. The second and third are related in that
some away- from- home recharging opportunities such as workplaces would most often be
used during the day ( when electricity rates would presumably be higher, especially
during afternoons and early evenings, under time- of- day electricity tariffs). PHEV drivers
would then face countervailing signals— maximizing their PHEV benefits by plugging in
more, but having to pay a higher price than nighttime electricity in order to do so. In
short, the recharging frequency data reported here is from households who can recharge
at home, whose recharging frequency is constrained by a general lack of away- from-home
recharging opportunities created by the lack of both physical infrastructure and
social norms, but unconstrained by differential electricity prices.
We calculate the mean number of times per day each household plugged- in their PHEV
on weekdays and weekend days and plot the resulting frequency distributions in Figure
17. As explained above, the figures are based on only the final week of each household’s
experience with the PHEV- conversion. The weekday distribution ranges from zero to 2.6
instances of plugging- in per day. ( The zero- value for weekdays is from one household
who determined that recharging made too little difference ( compared to the substitution
of an HEV into their household fleet) to make it worthwhile.)