How green is an electric car? Are they truly environmentally friendly, or is it just greenwash? Electric car enthusiasts are always keen to point out the fact that their cars do not emit any pollution where they are being used. Detractors point to the coal-fired power station generating the electricity in the first place.
Both groups are making a valid point but, taken in isolation, both groups are wrong. Without looking at the whole picture, no fair assessment of the relative merits and disadvantages of different technologies and vehicle types can be made.
Current comparisons between conventionally powered cars and electric cars fail, because they typically only measure the 'tank to wheel' emissions of the exhaust from a car. Both the European Commission and the US Environmental Protection Agency has defined a standard set of tests for measuring these emissions. They measure the emissions from the point the fuel has been pumped into a fuel tank to the point where the energy is used. Of course, electric cars benefit significantly from this measurement because by themselves they do not pollute at all: all the pollution happens at the power station where the electricity is generated.
However, in the same way that a 'tank-to-wheel' measurement does not measure the true carbon footprint of using an electric car, neither does it measure the true carbon footprint of using a conventional combustion engine car.
For a conventional car, the carbon footprint for extracting, refining and transporting the oil needs to be taken into account, not just the carbon footprint for the emissions coming out of the tailpipe.
For an electric car, the carbon footprint for getting the raw fuel, transporting it to the power station, generating the electricity and 'delivering' it to the plug needs to be taken into account.
These measurements are called 'well-to-wheel' measurements. In order to be able to make a true comparison between electric cars and combustion engine cars, we need to be able to identify this well-to-wheel calculation for both oil use and electricity use.
There are several measurements that need to be considered when comparing the environmental impact of a conventional car with an electric car:
In a nutshell, when you take into account the sourcing and refining of oil, the full 'well-to-wheel' carbon emissions of a conventional car are around 20% higher than the official 'tank-to-wheel' emissions. Likewise, for electricity production, the emissions for sourcing the fuel and the transmission losses add around 15% to the official carbon emissions of the power stations. You also need to factor in the carbon footprint for the construction and eventual decommissioning of the power station and for the battery use in the electric car (which is typically around 1g CO2 for every kilometer travelled).
If you want to know how these figures are calculated, The Electric Car Guide - 2015 Edition covers this in detail, looking at all the different aspects of pollution, fuel refining and the different types of electricity power generation. The chapter also looks at the environmental impact of electric vehicle batteries and end-of-life recycling of both electric cars and conventional vehicles.
The amount of pollution generated by electricity production varies throughout the day, depending on supply and demand and where our electricity is sourced.
If you are based in the United Kingdom, this information is published in real time, so you can identify the carbon footprint of the electricity being used in the United Kingdom. The information is updated every five minutes throughout the day.
To identify the carbon footprint for charging and using an electric car in the United Kingdom right now, and see how it compares to a selection of conventionally powered cars, visit our Electric Car Carbon Footprint page.
Because it is possible to monitor the energy production in real time, it is possible for electric car owners to choose when to charge up their cars, charging their cars up when demand and the carbon footprint of electricity is low and avoiding charging up when the carbon footprint is higher.
We have created a free phone app that puts that information in the palm of your hands. eCO2 tells you the current carbon footprint of the electricity generated in the UK and shows you where it comes from. It will also tell you the carbon footprint of charging up your electric car, allowing you to choose when to charge up your car in order to get the lowest carbon footprint for your driving.
eCO2 takes into account the carbon impact of mining and transportation of the base fuels, the running costs of the power stations, the decommissioning cost of nuclear power and the construction impact of new power stations. It takes into account transmission losses (the average loss of energy through electricity cables between the power stations and our homes) in order to give the most accurate carbon footprint of any calculator available today.
eCO2 is now available on Google Play. It will be available on the App Store for iPhone and the Windows 8 Phone store in the next few days: