It's a very reasonable question: electric cars themselves have no tailpipe emissions, but what about the power plants used to recharge them?
After more than a dozen studies and five-plus years of plug-in car sales, we know the answer.
In North America, an electric car charged on even the dirtiest, most coal-intensive electric grid in the nation has wells-to-wheels carbon emissions no higher than that of a very fuel-efficient car.
DON'T MISS: Are Electric Cars Really Bad For The Planet? Simple Math Says No (Feb 2012)
In the best of cases, electric cars charged on very clean grids have such low carbon emissions associated with using them that no car with a combustion engine can come anywhere near to competing.
Now another study has proven the point, this one from the Great Plains Institute, looking only at conditions in the state of Minnesota.
Greenhouse-gas emissions for electric vs gasoline cars in Minnesota [Great Plains Institute]
The study concludes that running an average gasoline car in the state for a lifetime of 160,000 miles produces 465 grams of greenhouse-gas emissions for each of those miles.
About three-quarters of Minnesota's gasoline supply is derived from oil-sands petroleum in Alberta, which has a far higher carbon footprint than crude oil from other sources.
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For an electric car charged on electricity generated from the fuel mix used by energy provider Xcel Energy, that number is only 183 g/mi, or less than 40 percent of the carbon emissions.
The study also looked at the emissions associated with electric cars charged via electricity from the Midcontinent Independent System Operator (MISO) system, which manages the distribution of electricity across a number of states in the region.
Lifecycle greenhouse-gas emission for electric vs gasoline cars, Minnesota [Great Plains Institute]
On that mix, which includes more fossil fuels, the number rises to 268 g/mi of greenhouse gases, still a substantial reduction from the gasoline figure.
Should electric-car drivers in Minnesota choose to opt into fully renewable electricity supplies—as more than half do, according to the Institute's survey—associated emissions plummet to just 21 g/mi.
That's a mere 4 percent of the figure for the gasoline car, all of it from vehicle manufacturing.
CHECK OUT: New Study Doesn't Say 'Electric Cars Aren't Green'—Headlines To The Contrary (Dec 2014)
The study's conclusion underscores just how advantageous electric cars are to the atmosphere:
So the next time you hear the phrase "coal tailpipe," now you have facts and data with which to set that person straight.
Especially if he or she lives in Minnesota.