Charging Electric Cars from the Grid: A Good Choice – or the Best Choice for Lowering Global Warming Emissions?

April 19, 2012
Laura Wisland
Former contributor

Electric vehicles, hailed by some as the greenest cars on the planet, have also been dismissed by others as an expensive way to do little more than move vehicle emissions from the tailpipe to a smokestack. So who’s got it right? My colleague, Amine Mahmassani, who works in the Clean Vehicles program at UCS recently co-authored a new report on electric vehicles which clears the air on the issue. I interviewed Amine to see what I could learn about global warming emissions from charging vehicles on the electricity grid.

Given today’s vehicle market, is buying an electric vehicle really a good option for the climate conscious driver?

The answer is yes, but just how good depends on where in the country you live.

This post is part of a series on the UCS report State of Charge: Electric Vehicles’ Global Warming Emissions and Fuel-Cost Savings Across the United States.

The global warming pollution emitted when charging your electric vehicle depends on how much of the electricity of your area is powered by coal, and how much comes from cleaner alternatives such as renewable sources and natural gas. Even on the most coal-heavy grids, EVs are on par with the most fuel-efficient conventional gasoline vehicles for global warming emissions – making them a good choice, though not necessarily the best. Only in areas where a greater share of electricity comes from cleaner sources do EVs compete with good gasoline-hybrids; in many cases beating even the most fuel-efficient hybrids on the road for global warming emissions.

Can one determine how electric vehicle emissions compare in different parts of the country?

The U.S. can be divided into 26 electric grid regions, each with a unique mix of power generation resources. We performed an analysis of the global warming emissions produced when charging an electric vehicle in each region, and then placed the regions into three categories—Good, Better, and Best—based on how the emissions compare to those of gasoline-powered vehicles. For example:

  • EVs in Good regions produce the same global warming emissions per mile as a gasoline vehicle with a fuel economy somewhere between 31 and 40 mpg. This means that their emissions are comparable to the best non-hybrid gasoline models available, such as the Ford Fiesta and the Hyundai Elantra.
  • EVs in Better regions produce the same global warming emissions per mile as a gasoline vehicle with a fuel economy somewhere between 41 and 50 mpg. This means that their emissions are comparable to the best gasoline hybrid models available, such as the Toyota Prius and Honda Civic Hybrid.
  • EVs in Best regions produce the same global warming emissions per mile as a gasoline vehicle with a fuel economy somewhere in excess of 50 mpg. This means that they outperform the best gasoline hybrid models available.

To make sure we are taking the fuel’s full life-cycle into account, our analysis includes emissions not just from burning fuel to power a car or to generate electricity, but also from producing the fuel. So we include emissions from pumping and refining oil into gasoline as well as mining and transporting coal, for example.

Check out the map to see how EVs in your region stack up. Click on the image for a larger version.

So what are the results? Where are the “Best” regions for charging an electric vehicle?

The analysis shows that 45% of Americans live in regions where electric vehicles are the “best” choice, producing less global warming pollution than any gasoline vehicle on the road, including the best hybrids. For those that don’t, EVs are at least a “good” choice, producing significantly less global warming pollution than the average new compact car.

So if you want to buy an EV and you live in a region with a “dirtier” electricity grid, what do you recommend?

Well first, it is important to note that the electricity grid has been getting cleaner as older coal plants are retired, and investments in cleaner power from renewables and natural gas increase. So even if an EV purchased today may not be the very best choice for cutting global warming pollution where you live right now, its emissions are likely to improve over its lifetime.

But there are definitely some things people can do right now to improve the environmental performance of EVs in their region. By participating in green energy programs offered by their utilities, supporting renewable energy standards for their state, or even producing their own renewable energy with rooftop solar panels if they own a home, individuals can help electric vehicles live up to their potential as the best choice everywhere.