The long tailpipe
The long tailpipe is a reference to greenhouse gases that are emitted in the production of electricity used to charge electric vehicles. Plug-in electric vehicles operating in all-electric mode have no emissions (greenhouse gases or otherwise) from the onboard source of power. The long tailpipe claims these emissions are shifted from the vehicle tailpipe to the location of the electrical generation plants. From the point of view of a well-to-wheel assessment, the extent of the actual carbon footprint depends on the fuel and technology used for electricity generation.
Plug-in electric vehicles operating in all-electric mode do not emit greenhouse gases from the onboard source of power but emissions are shifted to the location of the generation plants. From the point of view of a well-to-wheel assessment, the extent of the actual carbon footprint depends on the fuel and technology used for electricity generation. From the perspective of a full life cycle analysis, the electricity used to recharge the batteries must be generated from renewable or clean sources such as wind, solar, hydroelectric, or nuclear power for PEVs to have almost none or zero well-to-wheel emissions. On the other hand, when PEVs are recharged from coal-fired plants, they usually produce slightly more greenhouse gas emissions than internal combustion engine vehicles and higher than hybrid electric vehicles.
Because plug-in electric vehicles do not produce emissions at the point of operation are often perceived as being environmentally friendlier than vehicles driven through internal combustion. Assessing the validity of that perception is difficult due to the greenhouse gases generated by the power plants that provide the electricity to charge the vehicles' batteries. For example, the New York Times reported that a Nissan Leaf driving in Los Angeles would have the same environmental impact as a gasoline-powered car with79 mpg‑US (3.0 L/100 km; 95 mpg‑imp) compared to the same trip in Denver would only have the equivalent of 33 mpg‑US (7.1 L/100 km; 40 mpg‑imp). The U.S. Department of Energy published a concise description of the problem: "Electric vehicles (EVs) themselves emit no greenhouse gases (GHGs), but substantial emissions can be produced 'upstream' at the electric power plant."
Carbon footprint in selected countries
A study published in the UK in April 2013 assessed the carbon footprint of plug-in electric vehicles in 20 countries. As a baseline the analysis established that manufacturing emissions account for 70 g CO2/km. The study found that in countries with coal-intensive generation, PEVs are no different from conventional petrol-powered vehicles. Among these countries are China, Indonesia, Australia, South Africa and India. A pure electric car in India generates emissions comparable to a 20 mpg‑US (12 L/100 km; 24 mpg‑imp) petrol car. The country ranking was led by Paraguay, where all electricity is produced from hydropower, and Iceland, where electricity production relies on renewable power, mainly hydro and geothermal power. Resulting carbon emissions from an electric car in both countries are 70 g CO2/km, which is equivalent to a 220 mpg‑US (1.1 L/100 km; 260 mpg‑imp) petrol car, and correspond to manufacturing emissions. Next in the ranking are other countries with similar low carbon electricity generation, including Sweden (mostly hydro and nuclear power ), Brazil (mainly hydropower) and France (predominantly nuclear power). Countries ranking in the middle include Japan, Germany, the UK and the United States.
The following table shows the emissions intensity estimated in the study for each of the 20 countries, and the corresponding emissions equivalent in miles per US gallon of a petrol-powered car:
|Country comparison of full life cycle assessment
of greenhouse gas emissions resulting from charging plug-in electric cars and
emissions equivalent in terms of miles per US gallon of a petrol-powered car
carbon dioxide equivalent
emissions per electric car
expressed in (CO2e/km)
in terms of mpg US
of petrol-powered car
|Paraguay||70||Low carbon||218 mpg‑US (1.08 L/100 km)||Hybrid
|Iceland||70||217 mpg‑US (1.08 L/100 km)|
|Sweden||81||159 mpg‑US (1.48 L/100 km)|
|Brazil||89||134 mpg‑US (1.76 L/100 km)|
|France||93||123 mpg‑US (1.91 L/100 km)|
|Canada||115||Fossil light||87 mpg‑US (2.7 L/100 km)||Beyond
|Spain||146||61 mpg‑US (3.9 L/100 km)|
|Russia||155||57 mpg‑US (4.1 L/100 km)|
|Italy||170||Broad mix||50 mpg‑US (4.7 L/100 km)||New
|Japan||175||48 mpg‑US (4.9 L/100 km)|
|Germany||179||47 mpg‑US (5.0 L/100 km)|
|United Kingdom||189||44 mpg‑US (5.3 L/100 km)|
|United States||202||Fossil heavy||40 mpg‑US (5.9 L/100 km)||Efficient
|Mexico||203||40 mpg‑US (5.9 L/100 km)|
|Turkey||204||40 mpg‑US (5.9 L/100 km)|
|China||258||Coal based||30 mpg‑US (7.8 L/100 km)||Average
|Indonesia||270||28 mpg‑US (8.4 L/100 km)|
|Australia||292||26 mpg‑US (9.0 L/100 km)|
|South Africa||318||24 mpg‑US (9.8 L/100 km)|
|India||370||20 mpg‑US (12 L/100 km)|
|Note: Electric car manufacturing emissions account for 70 g CO2/km
Source: Shades of Green: Electric Cars’ Carbon Emissions Around the Globe, Shrink That Footprint, February 2013.
Carbon footprint in the United States
In the case of the United States, the Union of Concerned Scientists (UCS) conducted a study in 2012 to assess average greenhouse gas emissions resulting from charging plug-in car batteries from the perspective of the full life-cycle (well-to-wheel analysis) and according to fuel and technology used to generate electric power by region. The study used the Nissan Leaf all-electric car to establish the analysis baseline, and electric-utility emissions are based on EPA's 2007 estimates. The UCS study expressed the results in terms of miles per gallon instead of the conventional unit of grams of greenhouse gases or carbon dioxide equivalent emissions per year in order to make the results more friendly for consumers. The study found that in areas where electricity is generated from natural gas, nuclear, hydroelectric or renewable sources, the potential of plug-in electric cars to reduce greenhouse emissions is significant. On the other hand, in regions where a high proportion of power is generated from coal, hybrid electric cars produce less CO2 equivalent emissions than plug-in electric cars, and the best fuel efficient gasoline-powered subcompact car produces slightly less emissions than a PEV. In the worst-case scenario, the study estimated that for a region where all energy is generated from coal, a plug-in electric car would emit greenhouse gas emissions equivalent to a gasoline car rated at a combined city/highway driving fuel economy of 30 mpg‑US (7.8 L/100 km; 36 mpg‑imp). In contrast, in a region that is completely reliant on natural gas, the PEV would be equivalent to a gasoline-powered car rated at50 mpg‑US (4.7 L/100 km; 60 mpg‑imp).
The following table shows a representative sample of cities within each of the three categories of emissions intensity used in the UCS study, showing the corresponding miles per gallon equivalent for each city as compared to the greenhouse gas emissions of a gasoline-powered car:
|Regional comparison of full life cycle assessment
of greenhouse gas emissions resulting from charging plug-in electric vehicles
expressed in terms of miles per gallon of a gasoline-powered car with equivalent emissions
by emissions intensity
miles per gallon
carbon dioxide equivalent
(CO2e) emissions per year
expressed as mpg US
|Percent reduction in
27 mpg US average
new compact car
|Combined EPA's rated
fuel economy and
Lowest CO2e emissions
over50 mpg‑US (4.7 L/100 km)
|Juneau, Alaska||112 mpg‑US (2.10 L/100 km)||315%||2012 Toyota Prius/Prius c
50 mpg‑US (4.7 L/100 km)
|San Francisco||79 mpg‑US (3.0 L/100 km)||193%|
|New York City||74 mpg‑US (3.2 L/100 km)||174%|
|Portland, Oregon||73 mpg‑US (3.2 L/100 km)||170%||Greenhouse gas emissions (grams/mile)|
|Boston||67 mpg‑US (3.5 L/100 km)||148%||Tailpipe CO2||Upstream GHG|
|Washington, D.C.||58 mpg‑US (4.1 L/100 km)||115%||178 g/mi (111 g/km)||44 g/mi (27 g/km)|
Moderate CO2e emissions
equivalent to between
41 mpg‑US (5.7 L/100 km) to
50 mpg‑US (4.7 L/100 km)
|Phoenix, Arizona||48 mpg‑US (4.9 L/100 km)||78%||2012 Honda Civic Hybrid
44 mpg‑US (5.3 L/100 km)
|Miami||47 mpg‑US (5.0 L/100 km)||74%|
|Houston||46 mpg‑US (5.1 L/100 km)||70%||Greenhouse gas emissions (grams/mile)|
|Columbus, Ohio||41 mpg‑US (5.7 L/100 km)||52%||Tailpipe CO2||Upstream GHG|
|Atlanta||41 mpg‑US (5.7 L/100 km)||52%||202 g/mi (125 g/km)||50 g/mi (31 g/km)|
Highest CO2e emissions
equivalent to between
31 mpg‑US (7.6 L/100 km) to
40 mpg‑US (5.9 L/100 km)
|Detroit||38 mpg‑US (6.2 L/100 km)||41%||2012 Chevrolet Cruze
30 mpg‑US (7.8 L/100 km)
|Des Moines, Iowa||37 mpg‑US (6.4 L/100 km)||37%|
|St. Louis, Missouri||36 mpg‑US (6.5 L/100 km)||33%||Greenhouse gas emissions (grams/mile)|
|Wichita, Kansas||35 mpg‑US (6.7 L/100 km)||30%||Tailpipe CO2||Upstream GHG|
|Denver||33 mpg‑US (7.1 L/100 km)||22%||296 g/mi (184 g/km)||73 g/mi (45 g/km)|
|Source: Union of Concerned Scientists, 2012.
Notes: The Nissan Leaf is the baseline car for the assessment, with an energy consumption rated by EPA at 34 kWh/100 mi or 99 miles per gallon gasoline equivalent (2.4 L/100 km) combined.
The ratings are based on a region's mix of electricity sources and its average emissions intensity over the course of a year. In practice the electricity grid is very dynamic, with the mix of
power plants constantly changing in response to hourly, daily and seasonal electricity demand, and availability of electricity resources.
The long tailpipe has been the target of criticism, ranging from claims that many estimates are methodologically flawed to estimates that state that electricity generation in the United States will become less carbon-intensive over time. Tesla Motors CEO Elon Musk published his own criticism of the long tailpipe. The extraction and refining of carbon based fuels and its distribution is in itself an energy intensive industry contributing to CO2 emissions. In 2007 U.S. refineries consumed 39353 million kWh, 70769 million lbs of steam and 697593 million cubic feet of Natural Gas. And the refining energy efficiency for gasoline is estimated to be, at best, 87.7%.
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- "Compare side-by-side". U.S. Department of Energy and U.S. Environmental Protection Agency. 2012-04-13. Retrieved 2012-04-15. Energy and Environment tab: cars selected Toyota Prius, Prius c, Honda Civic Hybrid, and Chevrolet Cruze automatical, all model year 2012.
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- Greenhouse Gas Emissions for Electric and Plug-In Hybrid Electric Vehicles, web tool to estimate GHG by car model and zip code, U.S. Department of Energy and U.S. Environmental Protection Agency.
- Shade's of Green - Electric Car's Carbon Emissions Around the Globe, Shrink that Footprint, February 2013.
- State of Charge: Electric Vehicles' Global Warming Emissions and Fuel-Cost Savings across the United States, Union of Concerned Scientists, April 2012.