New Numbers Are In and EVs Are Cleaner Than Ever

May 31, 2017
David Reichmuth
Senior Engineer, Clean Transportation Program

Update: The latest numbers > 

One of the most common questions I’m asked about electric cars is, “how clean are they?”

Five years ago, UCS answered this question, publishing its first look at the global warming emissions from electric vehicles (EVs) in our ‘State of Charge’ report.  In early 2017, the US EPA updated their data on emissions from electricity generation, now capturing power plant emissions through the end of 2014. How does this new data change our assessment of EVs?

For over 70 percent of Americans, driving an EV results in fewer emissions than even a 50 MPG gasoline vehicle.

We now find the overall global warming emissions from using an EV is significantly lower for most of the US. Several regions of the country showed significant decreases in emissions, as compared to our first EV emissions assessment.

When compared to our initial report on EV global warming emissions, the changes are impressive. That report used 2009 power plant data (the most current available in 2012) and placed only 9 of 26 regions in the ‘best’ category. Now 19 regions are in the best category with only 2 in ‘good’ regions. For example, the Northern Midwest region that includes Minnesota and Iowa improved from 39 MPG equivalent to 54 MPG and Eastern Wisconsin also jumped from ‘good’ at 40 MPG to our ‘best’ rating with emissions equal to 52 MPG gasoline cars.

Global warming emissions from electricity generation have fallen in since 2009 in many parts of the US, making EVs even cleaner. Check out the changes by region in the slider above. 

Based on where EVs have been bought to-date, the average EV in the US now produces emissions equivalent to a hypothetical gasoline car achieving 73 MPG.

Nearly half of the EVs sold to date have gone to California, where the average EV produces global warming emissions equal to a 95 MPG gasoline car. The next 5 states for EV sales (Georgia, Washington, New York, Florida, and Texas) account for 20 percent of US EV sales and are regions that have emissions ratings of 50 MPG or better.

Manufacturing emissions are important, but much less of a factor than fuel emissions.

The emissions estimates presented above compare the use of an EV compared to using a gasoline vehicle. However, there are also emissions associated with the production of these cars, and in general making EVs produces more emissions than a comparable gasoline car. We studied this issue in our “Cleaner Cars From Cradle to Grave” report in 2015 and found that the extra emissions from making an 80-mile range EV (compared to a similar gasoline car) are about 15% higher. However, this extra emissions ‘debt’ is quickly recovered by the savings that accrue while using the electric vehicle.

How quickly the emissions are recovered depends on where the car is charged, but for an EV the size of the Nissan LEAF, we found that break-even point occurs after 6 to 13 months of use (depending on electric grid region), well shorter than the likely lifespan of the car.

Choosing an electric car over an inefficient gasoline model is one of the most influential decisions a household can make to reduce emissions

For the average American, transportation makes up about a third of all household global warming emissions. And compared to some other sources of emissions, we have a great deal of control over how efficient a vehicle we choose. The average new gasoline vehicle in the US is rated at 25 MPG. On average, driving an EV (at 73 MPG equivalent emissions) would produce global warming emissions at less than half of the rate of the average new vehicle.

If you’re curious about how clean specific EVs would be where you live, check out our EV tool here. It’s recently been updated with our newest estimates of EV emissions, and we’ve also added many new EV models. If you are interested in the most efficient (and lowest emission) EV models, check out the Hyundai Ioniq BEV, Chevy Bolt, and BMW i3 BEV models.

Changes since our last report include generation, fuel production, and transmission efficiency.

Our initial assessment comparing gasoline vehicle emissions to those from electric vehicles were detailed in our 2012 State of Charge report. That report relied on the best data available at the time. This included estimates of power plant emissions and transmission losses from 2009 and also included the most recent estimates of ‘upstream’ emissions (such as coal mining and oil refining).

While we used the same analysis method as both the State of Charge and Cleaner Cars From Cradle to Grave  reports to generate these new emission estimates, the input data has changed.

The EPA estimates of power plant emissions in their eGRID database have been updated from 2009 data to 2014 data. In many cases, the emissions from power plants decreased, often due to reductions in coal-fired power and increases in renewable generation. However, some regions did show an increase. For example, in the Pacific Northwest, hydroelectric power output was reduced and fossil fuel plants supplied additional power.

The eGRID data also includes an updated method for calculating the losses attributed to the transmission and distribution of electric power from generators to the end user. This loss estimate is significantly lower than previous estimates, and therefore lowers the emissions attributed to EVs.

Finally, we also updated the estimates of emissions from ‘upstream’ sources like fuel extraction and refining. We used the most recent version of the GREET model from Argonne National Laboratory to estimate these emissions.

 

Most regions showed a decrease in emissions from electricity generation and distribution from 2009 to 2014. Red triangles indicate the total change in global warming emissions due to changes in generation sources, upstream emissions from fuel production, and losses in transmission and distribution of electricity from power plants to the end user.