Indirect emissions from electric vehicles: Emissions from electricity generation

Abstract

Carbon dioxide (CO2) emissions from passenger cars represent an important and growing contributor to climate change. Increasing the proportion of electric vehicles (EVs) in passenger car fleets could help to reduce these emissions, but their ability to do this depends on the fuel mix used in generating the electricity that energises EVs. This study analyzes the indirect well-to-wheels CO2 emissions from EVs when run in the US, the UK, and France and compares these to well-to-wheels emission data for a selection of internal combustion engine vehicles (ICEVs) and hybrid electric vehicles (HEVs). The study also compares the well-to-wheels emissions of the existing passenger car fleet in each country to a hypothetical EV fleet with the average electricity generation requirements of the three EVs considered in this analysis.

Full text

Carbon dioxide (CO2) emissions
from passenger cars represent an
important and growing contributor
to climate change. Increasing the
proportion of electric vehicles
(EVs) in passenger car fleets could
help to reduce these emissions,
but their ability to do this depends
on the fuel mix used in generating
the electricity that energises EVs.
This study analyzes the indirect
well-to-wheels CO2 emissions
from EVs when run in the US, the
UK, and France and compares
these to well-to-wheels emissions
data for a selection of internal
combustion engine vehicles
(ICEVs) and hybrid electric
vehicles (HEVs). The study also
compares the well-to-wheels
emissions of the existing
passenger car fleet in each
country to a hypothetical EV fleet
with the average electricity
generation requirements of the
three EVs considered in this
analysis.
Indirect Emissions from Electric Vehicles:
Emissions from Electricity Generation
by Aaron Holdway, Alex Williams, Oliver Inderwildi and Sir David King
Policy Brief
Tr an sp or t is o ne o f th e la rg es t a nd
fastest-growing contributors to
increased greenhouse gas
concentrations and the associated
climate change 1, 2. Globally, passenger
cars alone emit more than 6 percent of
anthropogenic carbon dioxide (CO2) 2,
the most abundant anthropogenic
greenhouse gas 3. Electric vehicles (EVs)
– vehicles which have onboard batteries
that are charged with grid electricity and
which have no tailpipe emissions – have
received significant attention in the past
two decades as a means of helping to
further reduce localised vehicle
emissions and mitigate the associated
health concerns. Consequently, policies
to increase the number of EVs on the
roads have become increasingly
common in industrialised countries in
recent years 4-6.
!Upstream emissions from power
plants that energise EVs, however, are
often neglected, and only recently
studies by Jacobson 7 and Arar 8 have
addressed this issue. These studies
conclude that an instantaneous
conversion of the US vehicle fleet to
battery power could bring a CO2
emission reduction of up to 58 percent,
and even greater reductions are
possible if electricity generated entirely
from renewable sources such as hydro,
solar, wind, or nuclear power is used 9.
The potential of EVs to reduce
greenhouse gas emissions depends on
the fuel mix used in the electricity
generation that charges the vehicles’
batteries, which can vary widely from
country to country, and within countries.
Consequently, the emissions from
electricity generation, and thus the
indirect CO2 emissions from EV use,
also vary widely across and within
nations.
!This study focuses on CO
2, the most
important contributor to anthropogenic
climate change 3. It examines these
indirect emissions from electric car
usage from well to wheels, comparing
across three major industrialised
countries in which the national
electricity grid is fed by different mixes
of renewable and fossil fuel sources:
the US, where coal has the largest share;
the UK, where natural gas has a share
nearly equal to coal; and France, where
nuclear power predominates. The
paper calculates the amount of
electricity required to run electric cars
and the CO2 emissions that result from
generating this electricity in the US, the
UK, and France in order to establish a
sensitivity analysis of indirect emissions
and electricity carbon footprint.
Moreover, this study compares these
indirect emissions to the well-to-wheels
CO2 emissions of some of the most
efficient ICEVs and HEVs – that is,
emissions from primary fuel extraction
to delivery to the vehicle fuel tank (well-
to-tank) and emissions from combustion
of the fuel (tank-to-wheels).
!The study also considers the increase
in net electricity consumption that could
occur if the entire passenger car* fleet in
each country was replaced with EVs.
Smith School of Enterprise
and the Environment
University of Oxford
Hayes House
75 George Street
Oxford
OX1 2BQ
United Kingdom
Dr Oliver Inderwildi
oliver.inderwildi@smithschool.ox.ac.uk
www.smithschool.ox.ac.uk
ISSN:2041-4897
DOI: 10.4210/ssee.pbs.2010.003
1
* “Passenger cars” does not include light-duty
trucks: SUVs, pickup trucks, and minivans with a
gross weight of up to 8500 pounds (3.9 metric
tons) in the US and 3.5 tons in the UK and France
(refs. 13, 25, 28). This study omits light-duty
trucks as there were, at the time of writing (April
2010), no commercially-available battery electric
options.

Electric power generators do not operate at full capacity all
the time. The average capacity factor, or plant load factor,
of electricity generation – that is, the ratio of net electricity
generation in a given period to the amount of electricity that
would be generated in that period if operating at full
nameplate capacity – is 48 percent in the US 10, 11, 52
percent in the UK 11, 12, and 55 percent in France 11, 13, 14.
Net electricity generation is less than the nominal capacity
of the grid – in the US and UK it is about 70 percent of
annual peak demand 10, 12 – because power stations must
be shut down periodically for maintenance and because
electricity demand is not constant over the course of a day
or year. The effect a large-scale introduction of EVs might
have on net electricity consumption, and the ability of the
grid to supply this, is considered below.
!A number of recent studies have looked at emissions
associated with plug-in hybrid-electric vehicles (PHEVs)
15-17. Most studies on the potential of EVs to reduce
greenhouse gas emissions compared to conventional
vehicle technologies are at least a decade old 18-21. As
previously mentioned, two exceptions are Jacobson 7 and
Arar 8. In a review of options for powering EVs and fuel cell
vehicles, Jacobson states that “The US could theoretically
replace all 2007 on-road vehicles with BEVs (battery
electric vehicles) powered by 73 000-144 000 5-MW wind
turbines, less than the 300 000 airplanes the US produced
during World War II,” resulting in a 33 percent reduction in
US CO2 emissions. Jacobson assumes that wind-
generated electricity is over 99 percent carbon-free and
that the plug-to-wheels efficiency of BEVs (75-86 percent)
is much greater than the average tank-to-wheels efficiency
of fossil-fuel vehicles (17 percent). Arar, using 2006 figures,
finds that an instantaneous conversion of the US fleet of
passenger cars and light-duty trucks to battery power
could bring a CO2 emission reduction of 58 percent. Arar
also attempts to estimate fleet emissions for 2020
assuming a 10 percent uptake in EVs per year from 2011
to 2020 but using the present fuel mix. He finds that the
2020 fleet would emit 36 percent less CO2 than if the
conversion to EVs had not taken place.
!The present study looks specifically at the electricity
usage and associated well-to-wheels CO2 emissions for
three battery EVs which, at the time of writing (April 2010),
were the only multi-passenger EVs available for sale in
more than a single country: the Tesla Roadster; the TH!NK
City; and the REVAi (marketed in the UK as the G-Wiz i).
The Tesla Roadster, from Tesla Motors of San Carlos,
California, has been available for purchase in the US since
2008 and from stores in Europe and Canada since 2009 ║.
The TH!NK City, from Think of Aurskog, Norway, has been
available in Norway since 2008, with plans for sales
elsewhere in Europe in 2009 and in the US from 2010 ‡.
The REVAi, from REVA Electric Car Company of Bangalore,
India, has been available since 2008 in India and several
European countries §. Unlike previous US-focused studies
7, 8, the present study focuses on the US, the UK, and
France. Moreover, by calculating indirect emissions from
electricity generation in France, a country with relatively
low-carbon grid electricity, the study explores the potential
for emissions reduction through decarbonisation of the
electricity sector.
Methods
Here we elaborate on the methodology used in the
calculations. Data used are given in the text.
"The average CO
2 emissions from electricity generation in
each country (Table 3) were calculated as follows:
Net electricity generation is defined here as electricity
generated by major power producers – that is, companies
whose main business is electricity generation – since
national CO2 emissions figures for electricity generation
refer only to major power producers. The US Energy
Information Administration’s Annual Energy Review
expressly excludes plants with a generator nameplate
capacity less than 1 MW 10.
!The well-to-wheels CO
2 emissions for the three EVs
considered in this study were calculated by summing well-
to-power-plant emissions and power-plant-to-wheels
emissions. Well-to-power-pla nt CO 2 emissions –
analogous to well-to-tank for ICEVs – are defined here as
emissions from primary fuel extraction (e.g., coal, oil, gas)
to delivery to the power plant for use in electricity
generation, including all intermediate steps (detailed in
Ta b le 6 ). Well-to-power-plant emissions fo r eac h EV in each
country were calculated from fuel efficiency data (Table 2),
the breakdown of total net electricity generation (Table 4),
and the well-to-power-plant emissions for each type of fuel
used in electricity generation (Table 6).
!Power-plant-to-wheels CO
2 emissions – analogous to
tank-to-wheels for ICEVs – are defined as emissions from
generation of electricity at the power plant to delivery to the
EV’s battery. Power-plant-to-wheels emissions for each EV
in each country were calculated from the fuel efficiency for
each EV (Table 2) and the average direct CO2 emissions
from electricity generation (Table 3).
"The sum of the well-to-power-plant (WtPP) and the
power-plant-to-wheels (PPtW) CO2 emissions for each EV
in each country (C) is the well-to-wheels (WtW) CO2
emissions (Table 5):
2
║ www.teslamotors.com/media/press_room.php: April 9, 2008, and
March 3, 2009. All websites in this paper were accessed August 1, 2009.
‡
www.think.no/think/Press-Pictures/Press-releases: March 12, March 18,
and May 6, 2009
§ www.revaindia.com/revaworldwide.htm

"
!Analogously, well-to-wheels CO
2 emissions for the ICEVs
and HEVs (Table 9) are the sum of well-to-tank emissions,
defined as emissions from primary fuel extraction to
delivery to vehicle fuel tank, and tank-to-wheels emissions,
defined as emissions from combustion of the fuel. The
tank-to-wheels data are from the UK Government’s Vehicle
Certification Agency (VCA); the well-to-tank figures were
calculated from fuel efficiency figures from the VCA and
the literature value for oil in Table 6, taken to be the same
for well-to-tank as for well-to-power plant. The well-to-tank
emissions (75 g/kWh) are comparable to those from Silva
et al. 22, who report 51.1 g/kWh for well-to-tank
greenhouse gas emissions for diesel.
"The well-to-wheels CO
2 emissions of the hypothetical EV
fleet in each country is the average of each row in Table 5.
The average well-to-wheels CO2 emissions for the existing
passenger car fleets in each country were calculated from
the net calorific value of fuel consumed by the fleet, the
number of vehicle kilometres driven, the literature value for
oil in Table 6, and fleet tailpipe CO2 emissions.
Results and Discussion
EVs
Ta b le 1 c o m pa r es k ey c ha r a c te r i st i c s o f e a c h o f t h e t h r ee
EVs included in this study (see Tables and Figures). The
amount of electricity generation required to run each of the
three EVs in each of the three countries considered in this
analysis is shown in Table 2 ¶.
Ta bl e 2. Amount of electricity required to run EVs (kWh/km) a
Tesla Roadster
TH!NK City
REVAi
US 10
0.21
0.18
0.15
UK 12
0.21
0.19
0.15
France 14
0.21
0.18
0.15
a
!All vehicle data are from www.teslamotors.com, www.think.no, and
www.revaindia.com, except a personal communication from M. Boxwell
(REVA G-Wiz [REVAi] Owners’ Club) stating that the REVAi’s loss due to
charging inefficiency is 13 percent.
The figures are inclusive of electricity transmission and
distribution losses and battery charging inefficiency.
"The average CO
2 emissions from electricity generation in
the same countries are shown in Table 3 (see Methods for
details on calculations).
Ta bl e 3. Average CO2 emissions from electricity generation
(g CO2/kWh)
Average Emissions
US 10, 36
605
UK 12, 37
543
France 14, 38
88
These figures can be interpreted in part through the share
of electricity in each country that is generated from fossil
fuels: 71 percent in the US, 77 percent in the UK, and just
10 percent in France 10, 12, 14. The carbon intensity of the
UK’s electricity generation is less than that of the US
despite the UK having a greater share of its electricity
generation coming from fossil fuels. This is because, as
shown in Table 4, the US has a greater share of coal in its
fuel mix, while the UK has a greater share of natural gas.
Coal produces approximately twice as much CO2 per kWh
as natural gas 12.
Ta bl e 4. Breakdown of total net electricity generation
(GWh / percent of net electricity generation)
Coal
Oil
Natural
Gas
Nuclear
RES/
Other a
Net Elec.
Gen. b
US 10
1 990 900
49.0
64 400
1.6
813 000
20.0
787 200
19.4
409 500
10.1
4 065 000
100.0
UK 12, c
136 173
40.1
2 727
0.8
122 232
36.0
68 248
20.1
9 903
2.9
339 283
100.0
France
14, c
21 302
3.9
5 005
0.9
19 494
3.6
422 854
78.1
72 673
13.4
541 327
100.0
a
!“RES” refers to renewable energy sources; “Other” fuel includes other
gases and non-renewable waste, amounting to less than 2 percent of net
electricity generation in each country.
b"Percentages may not add to totals due to rounding.
c
"Gross figures have been converted to net by removing electricity used
in pumping for pumped storage.
"The well-to-wheels CO
2 emissions for the three EVs
considered in this study are shown in Table 5.
Ta bl e 5. Average well-to-wheels CO2 emissions for EVs
(g CO2/km) (Tables 2, 3, 4, 5)
Tesla Roadster
TH!NK City
REVAi
US
141
126
102
UK
130
116
93
France
26
23
19
As this table demonstrates, the fuel mix in the national
electricity grid is the overwhelming factor in determining the
indirect well-to-wheels CO2 emissions from electric
vehicles (see Figure 1).
3
¶ All data in this study are for 2006, the last year for which all data were
available.

Fig. 1. Average well-to-wheels CO2 emissions for EVs (g CO2/km)
plotted from the data in Table 5
0!
20!
40!
60!
80!
100!
120!
140!
160!
REVAi!
TH!NK City!
Tes l a R o a d s t e r !
g CO2/km!
France!
UK!
US!
In the US and the UK, the emissions for the TH!NK City and
the Tesla Roadster are not appreciably lower than those of
the most efficient small diesel cars, as shown below.
France, however, with 78 percent of its electricity coming
from nuclear (Table 4), would find substantial emissions
reductions from passenger cars if it were to replace a large
part of its fleet with EVs. The well-to-power-plant CO2
emissions associated with nuclear power generation are
less than half the average of coal, oil, and natural gas (Table
6), and the generation of electricity from nuclear fission
produces no CO2 emissions.
Ta bl e 6. Well-to-power-plant CO2 emissions by type of fuel used
in electricity generation (g CO2/kWh) a
Coal 39, b
Oil 40,c
Natural
Gas 39, d
Nuclear 7,e
Range
85-135
40-110
48-100
9-70
Mean f
110
75
74
40
a
"The well-to-power-plant CO2 emissions for hydro power (1.9 g CO2/
kWh) 41 are negligible and have been excluded. This figure does not
include methane emissions, which may occur in a flooded reservoir from
the anaerobic decomposition of biomass 40.
b"For coal, this includes mining and transport.
c
"For oil, this includes exploration, extraction, transportation, and
refinement.
d"For natural gas, this includes gas processing, venting wells, pipeline
operation (mainly compression), and system leakage in transportation and
handling 40.
e
"For nuclear, this consists of fuel conversion, enrichment, and
fabrication. Enrichment produces up to 95 percent of the CO2 emissions
from nuclear fuel processing. Emissions can vary greatly depending on
the specific enrichment process employed.
f"Used in all calculations
ICEVs and HEVs
The figures from Table 5 can be compared to well-to-
wheels CO2 emissions data for a selection of ICEVs and
HEVs, as shown in the overall comparison, Table 9 (EV data
are shaded; ICEV and HEV data are unshaded).
!Table 9 underlines the importance of comparing the
vehicles on a well-to-wheels basis. By simply looking at
tank-to-wheels or the analogous power-plant-to-wheels,
the lowest-emitting car besides the EVs running in France
and the REVAi running in the UK, would be the Smart
fortwo cdi at 88 g CO2/km †. The next six ICEVs and HEVs
in Table 9 would all come ahead of the Tesla Roadster
running in the US. A well-to-wheels analysis, however,
demonstrates that EVs generally produce less CO2
emissions than comparable ICEVs or HEVs. The Tesla
Roadster fares well against comparable ICEVs such as the
Lotus Elise and the Porsche Boxster, both of which have
well-to-wheels emissions approximately double those of
the Tesla Roadster in the US.
!The well-to-tank CO
2 emissions for the ICEVs and HEVs
in Table 9 range from 25 to 64 g/km. The analogous well-
to-power-plant emissions for the three EVs ranges from just
6 to 17 g/km, due to their superior fuel efficiency. Even
though the average efficiency of electricity generation and
supply to end users in the US, the UK, and France is only
30 percent, 34 percent, and 37 percent, respectively 10, 12, 23
– about the same as an efficient diesel engine 24 – these
EVs’ lower use of fuel means their emissions are lower
than comparable ICEVs or HEVs. The next section
examines a hypothetical move to replace the current ICEV
fleet in each country with EVs.
Fleets
The three EVs under analysis differ in size and power, and
the average of their emissions can be used to represent
those of a hypothetical EV fleet. If all passenger cars in
each country** were replaced with EVs with the average
electricity generation requirements of the Tesla Roadster,
TH!NK City, and REVAi (the three EVs considered in this
analysis), the fleet well-to-wheels CO2 emissions for each
country would be as found in Table 7. (The results are
based on the average CO2 emissions from electricity
generation from Table 3, which may change by the time
electric vehicles reach significant fleet penetration.)
Ta bl e 7. Average well-to-wheels CO2 emissions for hypothetical
EV fleets (Table 5) and existing passenger car fleets (g CO2/km).
Hypothethical EV fleet a
Existing fleet b
US
123
301
10, 27-29, 40
UK
113
223
12, 25, 37, 40
France
23
229
12, 13, 38, 40, 42
a
"The figures for the hypothetical EV fleets are the average of the well-to-
wheels CO2 emissions of the Tesla Roadster, TH!NK City, and REVAi.
b"Existing fleet figures are calculated from the net calorific value of fuel
consumed by the fleet, the number of vehicle kilometres driven, the
literature value for oil in Table 6, and fleet tailpipe CO2 emissions.
4
† www.vcacarfueldata.org.uk (UK Government’s Vehicle Certification
Agency)
** That is, the number of passenger cars registered in each country in
2006, the last year for which all study data were available.

"Table 7 also shows the average well-to-wheels CO
2
emissions for the existing passenger car fleets in each
country. Compared to the existing fleets, the hypothetical
EV fleets would produce 59 percent less CO2 emissions in
the US, 49 percent less in the UK, and 90 percent less in
France. The UK and French fleet figures are lower than that
of the US in part because of their greater use of diesel
vehicles, whose engines are more efficient than petrol
engines; the higher use of manual transmissions compared
to automatic; the smaller average car size; and the
traditionally stricter fuel efficiency standards 13, 25, 26. Even
considering the 2006 model year only, the US well-to-
wheels CO2 emissions would still be higher, at 234 g/km,
than those of the entire fleets in the UK and France 10, 27-29.
The difference would be even more marked if light-duty
trucks were included. Light-duty trucks, many of which are
used as passenger cars and include SUVs, pickup trucks,
and minivans, make up 42 percent of all light-duty vehicles
in the US, while accounting for only 10 percent in the UK
and 16 percent in France 13, 25, 28.
"Moving a large part of the ICEV fleet to EVs would require
a number of considerations. First, it may be difficult to get
consumers to move to smaller cars such as the TH!NK City,
and REVAi, particularly in the US, where, as mentioned
above, SUVs, pickup trucks, and minivans make up two-
fifths of the light-duty vehicle fleet. Second, EVs are still
more expensive than comparable ICEVs, despite tax
credits and other incentives (Table 1). Third, the average
vehicle lifetime in the US (for example) is about 15 years 30,
meaning that major fleet penetration, under the best
circumstances, would take many years 8. Fourth, emissions
reductions from taking ICEVs off the roads would be
partially offset by increased emissions from power plants,
although controlling emissions from a few thousand power
plants may be easier than controlling emissions from
millions of tailpipes. Fifth, a charging infrastructure and
concomitant government policies would be required.
Finally, if the entire fleet in each country (see footnote **)
were replaced with EVs with the average electricity demand
of the Tesla Roadster, TH!NK City, and REVAi, the increase
in net electricity consumption that would occur in each
country would be 12 percent in the US 10, 28, 20 percent in
the UK 12, 25, and 15 percent in France 13, 14. However, since
EVs are usually charged at night when demand is lower,
and most EVs would not have to be charged, or charged
fully, every night for average daily usage, the increase in
demand could potentially be met in part by maintaining
daytime electricity production levels overnight. In the UK,
for example, where charging the hypothetical EV fleet
would see a greater relative increase in electricity demand
than in the US or France, half of the additional demand
could potentially be met in this way, as shown in Figure 2,
without the need for additional electricity generation
infrastructure.
Fig. 2. Average electricity demand in the UK in 2006
(www.nationalgrid.com/uk/Electricity/Data), with half the demand
the full hypothetical UK EV fleet would bring.
!
!Furthermore, charging EVs in large numbers in this way,
in off-peak hours, could lead to improved load shapes,
reducing daily variability in electricity demand 15, 31. The
extent of this improvement may increase with the flexibility
offered by intelligent electricity grids 32 and the introduction
of EV batteries with shorter charging times. EVs could also
potentially return to the grid excess electricity stored in their
batteries during times of peak load and replace it with
electricity in off-peak hours 33. Under the status quo,
meeting the demand of the full hypothetical EV fleet along
with existing demand would require using approximately 66
percent of installed capacity 11, 12, 25,†† instead of the current
52 percent 11, 12. But an increase in demand for charging
EVs, if it happens, would come gradually, over many years,
and extra capacity could be added over time.
Overall comparison
The well-to-wheels CO2 emissions for EVs, a selection of
ICEVs and HEVs, and the hypothetical EV and existing
national fleets are compared in Table 9. This table
demonstrates that EVs generally emit less CO2 than
comparable ICEVs. The data also underline the importance
of the fuel mix in the electricity grid: the more electricity
generation from nuclear and renewable sources, the lower
the CO2 emissions associated with EV use.
!The data hide regional differences within each country,
however. In the US, for example, in twelve states more than
70 percent of in-state electricity generation comes from the
combustion of coal, while in four states more than 70
percent comes from nuclear and renewable sources ‡‡,¶¶.
At one extreme is North Dakota, where 94 percent of in-
5
†† www.nationalgrid.com/uk/Electricity/Data
‡‡ www.eia.doe.gov/cneaf/electricity/epa/generation_state.xls
¶¶ These figures are indicative only, as electricity in much of the US is
generated and transmitted on a regional basis, in regions that may span
several states and may not follow state boundaries.

state electricity generation comes from coal, and where
emissions from in-state electricity generation average 1012
g CO2/kWh §§. At the other extreme are states like Idaho,
which generates 84 percent of its in-state electricity from
hydroelectric, resulting in in-state electricity generation
emissions of just 65 g CO2/kWh 2§§. In the UK, 96 percent
of electricity generated by major power producers in
Northern Ireland comes from fossil fuels, while 37 percent
in Scotland is from nuclear and renewable sources 12. In
France, 99 percent of electricity generation in the region of
Île de France is from conventional thermal combustion,
while in eight other regions more than 95 percent of
generation is from nuclear and renewable sources 14.
"If the EVs in this study were to run in states or regions
where one fuel predominates, the results would be similar
to Table 8, which shows CO2 emissions for the three EVs if
running on just one fuel.
Ta bl e 8. Average well-to-wheels CO2 emissions for EVs (g CO2/
km) if using electricity generated from a single fuel (Tables 2, 4, 5), a
Tesla
Roadster
TH!NK City
REVAi
Hypothetical
EV fleet
Coal
212
189
153
185
Oil
155
138
111
135
Natural gas
101
90
73
88
Nuclear
8
7
6
7
a
"Using CO2 emissions estimates for electricity generation in the UK 12:
912 g/kWh for coal, 670 g/kWh for oil, and 412 g/kWh for natural gas.
These figures compare to well-to-wheels CO2 emissions of
234 g/km for passenger cars from the 2006 model year in
the US (see above, under Fleets). Thus, even though the
EVs may be running on electricity generated entirely from
coal, and even though the efficiency of electricity
generation and supply to end users in the US, the UK, and
France averages only 34 percent (see above), the EVs’
superior efficiency means they have lower well-to-wheels
emissions than the average ICEV. The EVs considered here
require 37 to 55 percent less energy per kilometre than the
most efficient ICEV or HEV in Table 9.
!Obtaining maximum environmental benefits from EVs,
however, requires decarbonising the electricity sector.
Changing the fuel mix is difficult due to long lead times
from planning to operation, combined with plant lifetimes of
up to 50 years. Jacobson suggests that nuclear, tidal,
wave, and hydroelectric may not be the best options
because their long lead times produce “opportunity cost
emissions” compared to technologies with the least delay:
solar-photovoltaics, concentrated solar, and wind, closely
followed by geothermal 7.
"Despite the environmental advantages mentioned above,
the number of EVs on the road remains small, most likely
due to cost and limited vehicle range. As of 2007, there
were approximately 4200 battery electric passenger cars
running in the US 34 and 1200 in the UK (P. Syron, UK
Department for Transport, personal communication).
Vehicle cost remains high at these low production volumes,
although those who cannot yet afford an EV would do well
to drive a fuel-efficient ICEV or HEV like those shown in
Ta bl e 9 . C o nt i n ue d im p ro v e m en t in I CE V te c h no l o gy i s
essential, as ICEVs will continue to dominate vehicle sales
for the foreseeable future.
Conclusions
Analyzing the indirect well-to-wheels CO2 emissions from
three production EVs has shown that EVs can reduce well-
to-wheels CO2 emissions over the existing fleet by more
than 90 percent. This suggests that EVs should be
particularly promoted where electricity generation is the
least carbon-intensive – as has been done, for example, in
California and France 4 – as the potential for EVs to reduce
CO2 emissions depends on the fuel mix used in generating
the electricity that powers them. The electricity grid must be
decarbonised if EVs’ full potential to reduce CO2 emissions
is to be realised: Decarbonisation of electricity production
should go hand-in-hand with the introduction of EVs.
Decisions on building new electricity generation capacity in
the coming years will affect the carbon intensity level of the
grid for decades to come and affect the potential for EVs to
greatly reduce CO2 emissions. In order to create a
comprehensive picture of the environmental benefits of
different vehicles and drivetrains, however, the cradle-to-
grave emissions of the vehicles themselves have to be
taken into account. The authors’ research group is currently
investigating these embedded emissions.
Acknowledgments
This work is part of the Future of Mobility project,
conducted at the Smith School of Enterprise and the
Environment, University of Oxford, and funded by Shell
International Petroleum Co. Ltd. We are grateful to Jack
Jacometti, Vice President, Future Fuels & CO2; Stewart
Kempsell, GM Business Development, Future Fuels & CO2;
Steve Skippon, Scientist, Shell Global Solutions (UK); and
Sylvia Williams, Business Development Manager, Global
XTL Development, for fruitful discussions, as well as our
Smith School colleague, Dr. Xiaoyu Yan.
Notes and references
a!Low-Carbon Mobility Centre, Smith School of Enterprise
and the Environment, University of Oxford, Hayes House, 75
George Street, Oxford, OX1 2BQ. Fax: +44 (0)1865 614960;
Te l: + 4 4 ( 0 )1 8 6 5 6 1 49 4 2 ; E - ma i l :
oliver.inderwildi@smithschool.ox.ac.uk
6
§§ www.eia.doe.gov/cneaf/electricity/epa/generation_state.xls and
emission_state.xls

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Ta bl e s an d fi g u re s
Ta bl e 1. EV characteristics a
Te sl a Ro a d st e r
TH!NK City
REVAi
Driving range, combined
"city/highway (km)
~354
175
80 (city only)
To p s p ee d (k m / h )
201
100
80
Peak power (kW)
185
30
13
Battery type
Lithium-ion
Lithium-ion or sodium
Lead acid
Battery capacity (kWh)
~53
28.3
9.6
Battery charging time (h),
"0-100% state of charge
3.5-48 b
13
8
Battery weight (kg)
450
245-260
~250
To ta l cu r b w e i g ht ( kg )
1238
1397
650 c
Base price (US$) d
109,000
~34,000
~14,000
a
"All data are from www.teslamotors.com, www.think.no, and www.revaindia.com, except where noted.
b!The charging time is 3.5 hours using Tesla’s High Power Connector; 8 hours using its 240-V Mobile Connector, the highest-
power portable charging option; and 37-48 hours using its 120-V Mobile Connector.
c
"The REVAi is classified as a quadricyle rather than a passenger car under European Parliament and Council Directive 2002/24/EC
35
d!Base price in the US (Tesla Roadster), Norway (TH!NK City: NOK 212 500), and the UK (REVAi: £8495; www.goingreen.co.uk/
store/pick_new [UK REVA retailer]); converted to US dollars on August 1, 2009, at www.xe.com/ucc.
COUNTRY
COUNTRY
EV Modelb
gCO2/km
HEV/ICEV Modelb
gCO2/km
UK
UK
REVAi
93
Smart fortwo (diesel)
112
EV Fleet
114
To yo t a P r i us T 3
118
TH!NK City
118
Seat Ibiza
126
Volks wagen P olo
127
To yo t a i Q
128
Te sl a Ro a d st e r
131
Smart fortwo (gasoline)
133
Honda Civic Hybrid
140
Mini Cooper Clubman
166
Lotus Elise
208
Existing Fleet
221
Porsche Boxster
284
FRANCE
FRANCE
REVAi
19
TH!NK City
23
EV Fleetd
23
Te sl a Ro a d st e r
27
Smart fortwo (diesel)e
112
To yo t a P r i us T 3 d
118
Seat Ibizae
126
Volks wagen P oloe
127
To yo t a i Q f
128
Smart fortwo (gasoline)f
133
Honda Civic Hybridd
140
Mini Cooper Clubmanf
166
Lotus Elisef
208
Existing Fleet
228
Porsche Boxsterf
284
US
US
REVAi
102
Smart fortwo (diesel)
112
To yo t a P r i us T 3
118
TH!NK City
123
EV Fleet
123
Seat Ibiza
126
Volks wagen P olo
127
To yo t a i Q
128
Smart fortwo (gasoline)
133
Honda Civic Hybrid
140
Te sl a Ro a d st e r
143
Mini Cooper Clubman
166
Lotus Elise
208
Porsche Boxster
284
Existing Fleet
361
Ta bl e 9 . Comparison of well-to-wheels CO2 emissions for EVs, hypothetical EV and existing fleets by country, and a
selection of current ICEVs and HEVs a.
a. www.vcacarfueldata.org.uk (UK Government’s Vehicle Certification Agency)
b. The 2009 model year is used for all. Except where noted, the fuel is gasoline and the gearbox is automatic.
c. The figure for the hypothetical EV fleets is the average of the fuel efficiency figures of the Tesla Roadster, TH!NK city, and REVAi.
d. HEV
e. ICEV Diesel
f. ICEV Gasoline
8
An abbreviated version of this Policy Brief will be published in Energy and Environmental Science, 2010