The question is a reasonable one: electric cars may be zero-emission, but what about the electricity to recharge them?
While renewable energy is growing globally, burning fossil fuels is still the source of most electric power today.
The good news is that in most areas of the U.S., the "wells to wheels" carbon-dioxide emissions associated with driving a mile in an electric car are far lower than those for the average car—and in many cases, than even the best 58-mpg hybrid model.
The standard map showing this in easily digestible format, converting those emissions to a miles-per-gallon equivalent, has been issued by the Union of Concerned Scientists based on the latest data available.
Now, however, another group has joined the fray: the Climate Central news service has published its own map, also based on data from the U.S. Energy Information Authority, that shows essentially the same thing.
We somewhat prefer the UCS map, because it shows the miles-per-gallon equivalencies.
Electric-car wells-to-wheels emission equivalencies in MPG, Sep 2015 [Union of Concerned Scientists]
That allows a Nissan Leaf or Tesla Model S driver to say confidently, "On the average grid in my state (or region), my car has a lower carbon-emission footprint than even a Hyundai Ioniq Hybrid Eco, the most fuel-efficient car sold in the U.S. this year without a plug."
Or words to that effect.
The Union of Concerned Scientists updates its map fairly regularly, and we'll replace the graphic above with newer information when it arrives.
READ THIS: In Just One Year, Electric Cars Have Gotten Cleaner: How'd They Do That? (Dec 2014)
But those year-to-year changes in MPG equivalencies—reflecting changes to the reported grid mix, generally in the direction of more natural gas and renewables, and less coal—give electric cars one unique facet that no combustion-engine car can match.
Electric cars actually get cleaner and cleaner as the grids used to recharge their batteries get cleaner.
Every time new EIA data is issued, the maps can be updated and the improvement in MPG equivalencies can be compared.
Chrome exhaust pipe
Over the six years electric cars have been sold in California, for instance, that state's grid has acquired more renewables—meaning every mile driven in a car charged on the California grid has less carbon associated with it than it did the prior year.
That's before the phenomenon, of course, of electric-car drivers installing home solar panels or paying a surcharge to their utilities for entirely renewable energy.
Under those circumstances, the wells-to-wheels carbon burden of an electric car is confined to its materials and manufacturing—which represent only a small fraction of the total energy used by a conventional car running on fossil fuels.
The issue of so-called criteria emissions and other pollutants associated with generating electricity is a separate issue, and another article altogether.
But on the climate-change emission front, electric cars are clearly, decisively better than the average new vehicle sold today (at roughly 25 mpg combined) and better in most places than even the best Prius or Ioniq hybrid.
[hat tip: NatureNut99]
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