How green are electric cars?
Norway, the world leader in electric car take-up, can boast that the vehicles are clean because they're almost exclusively run on hydropower. But how environmentally friendly is an electric car if its ultimate energy source is an oil-fired power plant?
Multiple studies have found that electric cars are more efficient, and therefore responsible for less greenhouse gas and other emissions than cars powered solely by internal combustion engines. An EU study based on expected performance in 2020 found that an electric car using electricity generated solely by an oil-fired power station would use only two-thirds of the energy of a petrol car travelling the same distance.
For every 100km travelled in a petrol car ...
... it takes 26 megajoules to get petrol out of the ground and transport it to the car ...
... and the car itself uses 142 megajoules to move itself around.
For the same distance in an electric car, using electricity generated in an oil-fired power plant
... it takes 74 megajoules to generate and transport the electricity to the car ...
... which then uses just 38 megajoules to move itself and its passengers
Although an electric car powered in this way is still ultimately burning the same fuel as the petrol car it replaces, it is burning much less of it. And although greenhouse gas emissions are similarly harmful wherever they occur, some other emissions which are harmful to human health are less dangerous when they happen at a power plant outside the city than at the roadside near schools and houses.
There are many different types of electric vehicle
The distinction between petrol and electric is not binary; a car's green credentials vary according to whether and how it uses electricity, and how that electricity is generated, with important trade-offs for efficiency and range.
Power source Petrol + Mains
Output mode Motor + Battery
A plug-in hybrid still uses internal combustion as its main power source, but can charge its internal battery from the mains. It is broadly-speaking midway between petrol and pure battery for efficiency, but has similar range to a petrol car. Its green credentials depend to a certain extent on how the mains electricity which it uses is generated. Choose a form of electricity generation (or a typical EU mix) to compare:
Greenhouse gas emissions
Energy used
How is electricity generated where I live?
In practice the ultimate source of your mains electricity is likely to be decided by the country you live in. Electric car drivers in Norway will mostly be using hydroelectric power (comparable to the "wind" category in the EU study); those in France, chiefly nuclear, and those in Germany and the UK, a mix of fossil and renewable, broadly comparable with the "EU-mix" figures. In the United States, the electricity source varies regionally; California uses a lot of renewables, while areas in the north-east are more likely to use fossil fuels including coal.
But what about the environmental effects of building the car?
A report by the Ricardo consultancy estimated that production of an average petrol car will involve emissions amounting to the equivalent of 5.6 tonnes of CO2, while for an average electric car, the figure is 8.8tonnes. Of that, nearly half is incurred in producing the battery. Despite this, the same report estimated that over its whole lifecycle, the electric car would still be responsible for 80% of the emissions of the petrol car. More recently, an FT analysis used lifecycle estimates to question the green credentials of electric cars, especially heavy ones.
Sources
The main figures are from the EU study Well-to-wheels analysis of future automotive fuels and powertrains in the European Context; the detailed estimates for a range of vehicle and fuel types are here. We have used the 2020 estimates for petrol vehicles and electrified petrol vehicles, using conventional petroleum/gasoline, and a small subset of electricity generation sources, for simplicity. The country energy mixes are from the World Bank. The lifecycle emissions estimates are from a Ricardo report for the Low Carbon Vehicle partnership.