So how do electric vehicles help to tackle climate change?

June 6, 2019

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, Zeke Hausfather’s piece on CarbonBrief.org 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

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).

Lifecycle greenhouse gas emissions for conventional and electric vehicles (by country) in grammes CO2-equivalent per kilometre, assuming 150,000 kilometres driven over the vehicle lifetime. Adapted from Figure 1 in Hall and Lutsey 2018. Details of the calculations are in the methods section at the end of the article. The error bars show a range of values for emissions from battery manufacture. Chart by Carbon Brief using Highcharts.

In most countries, the majority of emissions over the lifetime of both electric and conventional vehicles come from vehicle operation – tailpipe and fuel cycle – rather than vehicle manufacture. The exception is in countries – Norway or France, for example – where nearly all electricity comes from near-zero carbon sources, such as hydroelectric or nuclear power.

However, while the carbon emitted from burning a gallon of petrol or diesel cannot be reduced, the same is not true for electricity. Lifecycle emissions for electric vehicles are much smaller in countries such as France (which gets most of its electricity from nuclear) or Norway (from renewables).

The chart above bases electric-vehicle emissions on the current grid mix in each country. However, if the climate targets set in the Paris Agreement are to be met, electricity generation will become significantly less carbon-intensive, further increasing the advantage of electric vehicles over conventional ones.

by Anil George
Avid follower of all things tech. In between his quest for the ultimate gizmo, Anil fiddles with light meters, collects rare books and feeds his fetish for Jap horror movies. As Managing Editor of T3 Middle East for the GCC, Anil oversees content direction across print and digital. He was a CES 2020 Innovation Awards Judge, reprising his role as an Innovation Awards Judge at CES 2018, CES 2017, 2016 and 2015. Anil is also the Middle East's first Brand Ambassador for Ashdown Engineering. Reach him at: editor@t3me.com.