President Joe Biden took a big stand for clean energy at the end of 2021 when he committed to electric vehicles making up 50 percent of new car sales by 2030. As electric vehicles become cheaper and more energy-efficient, they should help offset greenhouse gas emissions from gas-guzzling vehicles. But without significant changes to the electricity sector, electric vehicles may not help the climate crisis as much as we think, according to a study published Monday in the journal Proceedings of the National Academy of Sciences. The findings call into question the capacity of electric vehicles to offset carbon dioxide emissions within our current energy system.
What’s new — The researchers found that without substantial changes to boost renewable energy, increased emissions to power electric vehicles under Biden’s plan will offset more than half of the emissions reductions from having fewer gasoline-powered vehicles.
Putting more electric vehicles on the road naturally leads to increased electricity demand. The fuel needed to generate electricity still comes mainly from two heavily polluting sources: natural gas and coal. In other words, more than half the gains of taking gas-powered cars off America’s highways will be lost if we don’t address the glaring issue of increased electricity demand.
Coal accounts for a significant portion of the emissions from electric vehicles. Coal generated only 24 percent of electricity in the U.S. but accounted for 61 percent of carbon dioxide emissions from 2019, according to the Environmental Protection Agency.
In many ways, the sustainable promise of electric vehicles in the U.S. depends on the future of coal — specifically, whether we can reduce our coal usage in the coming years.
“Our study illustrates how increasing demand for electricity — without complementary policies to promote more renewable sources of energy — is likely to increasingly come from coal-fired power plants,” Matthew Kotchen, a co-author on the study and a professor of economics at Yale University, tells Inverse.
Why it matters — To be clear, the researchers are not arguing against the adoption of electric vehicles. The study finds that adding roughly 60 million electric vehicles — and taking gas-powered vehicles off the roads — will result in somewhere between 171 to 235 million fewer metric tons of carbon dioxide emissions in 2030.
Kotchen says “those interested in purchasing EVs should still go for it, as they are generally better for the environment than gasoline-powered vehicles.”
But it’s important not to overstate the potential benefits of electric vehicles within our current energy system. According to the study, electricity demand for electric vehicles will increase carbon dioxide emissions somewhere between 104 and 114 million metric tons in 2030 — and coal is the primary culprit.
“We find that coal generation becoming more marginal is the key and [a] potential worry,” Kotchen says.
Simply shifting to electric vehicles without changing the source of the electricity for these cars will not accomplish the Biden administration’s climate goals.
“While electric vehicles are beneficial for the environment because they displace gasoline-fueled vehicles, their benefits depend on how clean the electricity is that is used to charged their batteries,” Kotchen says.
The research adds greater urgency to the need to shift away from coal and toward more renewable sources. The Biden administration pledged to decarbonize the electricity sector by 2035 and committed $5 billion to electric vehicle charging stations, but recent data also shows U.S. coal generation increased by 17 percent between 2020 and 2021.
How they made the discovery — While average emissions from the electricity sector have declined by 28 percent over the past decade, researchers felt that trend obscured a more disturbing factor: the seven percent increase in marginal emissions over the same time period.
Average emissions correspond to the general carbon intensity of emissions, but marginal emissions are what results from increased demand for electricity. For instance, our energy demands naturally ebb and flow corresponding with weather changes. Energy demands will go up on an unexpectedly chilly winter day in Texas or a hot spring afternoon in California as people turn on heaters and air conditioners. Unsurprisingly, global warming aligns with an increase in electricity consumption.
In the new study, the researchers sought to distinguish between the impact of average versus marginal emissions when determining the environmental impact of the Biden administration’s electric vehicle plan. They used statistical models to estimate marginal emissions — an overlooked factor when discussing climate impacts of the electricity sector.
“Our study is based on patterns that we actually observe over the last ten years on the electricity grid,” Kotchen says.
The researchers determined that relying on average emissions doesn’t paint an accurate picture of greenhouse gas emissions from the electricity sector. In fact, according to the study, the Biden administration's current electric vehicles plan overestimates emissions reductions from electric vehicles anywhere between 27 and 114 percent, depending on future climate policies and emission trends.
What’s next — The study advocates that coal must go if we are to achieve the sustainable future envisioned in Biden’s electric vehicle plan.
“We need to make sure that EVs do not become a lifeline for continued coal generation into the future,” Kotchen says.
While ramping up electric vehicle production will be necessary to transition the transportation sector to a greener future, we also need to focus on cleaner renewable energy sources — like solar and wind — for electricity generation.
“Without that, we will not be achieving the full potential of electric vehicles to help avoid emissions and reduce the impacts of climate change,” Kotchen says.