Update 7/2/2020: The lifecycle emissions figures were revised to reflect more recent data on electricity carbon intensity and battery manufacture.
Electric vehicles (EVs) are an important part of meeting global goals on climate change. They feature prominently in mitigation pathways that limit warming to well-below 2C or 1.5C, which would be inline with the Paris Agreement’s targets.
However, while no greenhouse gas emissions directly come from EVs, they run on electricity that is, in large part, still produced from fossil fuels in many parts of the world. Energy is also used to manufacture the vehicle – and, in particular, the battery.
Here, in response to recent misleading media reports on the topic, Carbon Brief provides a detailed look at the climate impacts of EVs. In this analysis, Carbon Brief finds:
EVs are responsible for considerably lower emissions over their lifetime than conventional (internal combustion engine) vehicles across Europe as a whole.
In countries with coal-intensive electricity generation, the benefits of EVs are smaller and they can have similar lifetime emissions to the most efficient conventional vehicles – such as hybrid-electric models.
However, as countries decarbonise electricity generation to meet their climate targets, driving emissions will fall for existing EVs and manufacturing emissions will fall for new EVs.
In the UK in 2019, the lifetime emissions per kilometre of driving a Nissan Leaf EV were about three times lower than for the average conventional car, even before accounting for the falling carbon intensity of electricity generation during the car’s lifetime.
Comparisons between electric vehicles and conventional vehicles are complex. They depend on the size of the vehicles, the accuracy of the fuel-economy estimates used, how electricity emissions are calculated, what driving patterns are assumed, and even the weather in regions where the vehicles are used. There is no single estimate that applies everywhere.
There are also large uncertainties around the emissions associated with electric vehicle battery production, with different studies producing widely differing numbers. As battery prices fall and vehicle manufacturers start including larger batteries with longer driving ranges, battery production emissions can have a larger impact on the climate benefits of electric vehicles.
Around half of the emissions from battery production come from the electricity used in manufacturing and assembling the batteries. Producing batteries in regions with relatively low-carbon electricity or in factories powered by renewable energy, as will be the case for the batteries used in the best-selling Tesla Model 3, can substantially reduce battery emissions.
Different studies find different results
A recent working paper from a group of German researchers at the thinktank Institute for Economic Research (ifo) found that “electric vehicles will barely help cut CO2 emissions in Germany over the coming years”. It suggests that, in Germany, “the CO2 emissions of battery-electric vehicles are, in the best case, slightly higher than those of a diesel engine”.
This study was picked up in the international media, with the Wall Street Journal running an editorial titled, “Germany’s dirty green cars”. It also engendered pushback from electric vehicle advocates, with articles in Jalopnik and Autoblog, as well as individual researchers rebutting the claim.
Other recent studies of electric cars in Germany have reached the opposite conclusion. One study found that emissions from EVs have emissions up to 43% lower than diesel vehicles. Another detailed that “in all cases examined, electric cars have lower lifetime climate impacts than those with internal combustion engines”.
These differences arise from the assumptions used by researchers. As Prof Jeremy Michalek, director of the Vehicle Electrification Group at Carnegie Mellon University, tells Carbon Brief, “which technology comes out on top depends on a lot of things”. These include which specific vehicles are being compared, what electricity grid mix is assumed, if marginal or average electricity emissions are used, what driving patterns are assumed, and even the weather.
The figure below, adapted from an analysis by the International Council for Clean Transportation (ICCT), shows an estimate of lifecycle emissions for a typical European conventional (internal combustion engine) car, the hybrid conventional car with the best available fuel economy (a 2019 Toyota Prius Eco), and a Nissan Leaf electric vehicle for various countries, as well as the EU average. [The Leaf was the top selling EV in Europe in 2018.]
The chart includes tailpipe emissions (grey), emissions from the fuel cycle (orange) – which includes oil production, transport, refining, and electricity generation – emissions from manufacturing the non-battery components of the vehicle (dark blue) and a conservative estimate of emissions from manufacturing the battery (light blue).