The cost of electric vehicle battery packs is falling so rapidly they are probably already cheaper than expected for 2020, according to a new study in Nature Climate Change.

Electric vehicles remain more expensive than combustion-engine equivalents, largely because of battery costs. In 2013 the International Energy Agency (IEA) estimated cost-parity could be reached in 2020, with battery costs reaching $300 per kilowatt hour of capacity.

But market-leading firms were probably already producing cheaper batteries last year, says today’s new research. It says its figures are “two to four times lower than many recent peer-reviewed papers have suggested.”

High costs, falling

Even though the  EU electric vehicle market grew by 37% year on year in 2014, it still made up less than 1% of total sales. High cost is a major reason why electric vehicles have failed to break through, alongside range and a lack of recharging infrastructure.

The new research is based on a review of 85 cost estimates in peer-reviewed research, agency estimates, consultancy and industry reports, news reports covering the views of industry representatives and experts, and finally estimates from leading manufacturers.

It says industry-wide costs have fallen from above $1,000 per kilowatt hour in 2007 down to around $410 in 2014, a 14% annual reduction (blue marks, below). Costs for market-leading firms have fallen by 8% per year, reaching $300 per kilowatt hour in 2014 (green marks).

Cost estimates and future projections for electric vehicle battery packs, measured in $US per kilowatt hour of capacity. Each mark on the chart represents a documented estimate reviewed by the study. Source: Nykvist et al. (2015).

For the market-leading firms, shown in green on the chart above, costs last year were already at the bottom end of projections for 2020 (yellow triangles).

The paper estimates prices will fall further to around $230 per kilowatt hour in 2017–18, “on a par with the most optimistic future estimate among analysts.” The crossover point where electric cars become cheapest depends on electricity costs, vehicle taxes, and prices at the pump.

In the US, with current low oil prices, battery packs would need to fall below $250 per kilowatt hour for electric cars to become competitive, the study says. Behavioural barriers to electric vehicle uptake present additional hurdles to widespread adoption.

The paper says:

“If costs reach as low as $150 per kilowatt hour this means that electric vehicles will probably move beyond niche applications and begin to penetrate the market more widely, leading to a potential paradigm shift in vehicle technology.”

Learning rate

To reach that level, costs will have to fall further. But a commercial breakthrough for the next generation of lithium batteries “is still distant,” the paper says, and many improvements in cell chemistry have already been realised. This seems to pour cold water on frequent claims ofnew battery types “transforming” the electric vehicle market.

However, there are still savings to be made in manufacturing improvements, industry learning, and economies of scale, which have already brought down costs in recent years. Cumulative global production and sales of electric vehicles are roughly doubling annually, the paper says.

That means the 30% cost reduction expected at Tesla Motors’ planned “Gigafactory” battery plant by 2017 represents a “trajectory close to the trends projected in this paper.” On the other hand, Renault-Nissan’s plans to build battery manufacturing capacity for 1.5 million cars by 2016 have hit the buffers as electric car sales have trailed expectations.

There are large uncertainties in the paper’s findings. Despite being the most comprehensive review to date, it relies on “sparse data” and acknowledges that a secretive industry might avoid revealing high costs, or conversely might subsidise battery packs to gain market share.

Overall it is “possible” that economies of scale will push costs down towards $200 kilowatt hour “in the near future even without further cell chemistry improvements,” the paper concludes. If the paper is right, then electric vehicle uptake could exceed expectations. That will be a good thing for the climate — just as long as the electricity that fuels them is not from coal.

Originally published on The Carbon Brief.