SHIFT: Sorry, critics — electric cars really are greener

I got the chance to drive the 2010 Tesla Roadster Sport earlier this week. Sitting behind the wheel, feeling the power of the all-electric motor, it was hard not to get caught up in the potential of electric vehicles (EVs). "Why aren't all vehicles electric?" I thought. "If we can build sporty, high-performance electric cars like the Tesla, surely we can make any car electric. Hell, we can make every car electric!"

Whoa. Slow down there, past me. Isn't that sleek EV you're driving just trading gasoline for other fossil fuels, taxing our very coal-heavy power grid? At least one person, Rutgers University professor Sunil Somalwar, is convinced the tradeoff isn't worth it, and he makes a convincing case here.

I don't agree with him, though. Why? Simple math.


Electric Vehicles' Power Demands

If every car in America went electric, it would mean all their fuel would come directly from the power grid (let's assume those solar-panel-roof and wind-turbine options are merely incidental). Just doing a little back-of-the-envelope math: A Tesla Roadster battery stores 53 kilowatt-hours (kWh) of energy. The Roadster's isn't a really a typical EV battery, though, and a better amount would probably be about half that — say, 25 kWh. Now multiply that by the number of vehicles on U.S. roads (about 250 million, according to the Department of Transportation) and you have about 6 billion kWh stored in all those theoretical batteries.

How often do those batteries need to be recharged? Considering our 25kWh battery, and with typical EVs getting about 2-3 miles per kWh, let's be conservative and say each one will need two full charges a week. So that's about 100 charges of the battery per year. So all those electric vehicles would use about 600 billion kWh a year.

The entire U.S. power grid generated a little over 4 trillion kWh in 2007, according the Energy Information Administration (EIA). A 600 billion kWh increase would be significant, but not unimaginable.


The Power Plant Dilemma

Nonetheless, 250 million EVs on the road would mean the country would need a lot of new power plants. With the majority of our power coming from coal, is that really a good idea? Sure, we could just assume we'll build a bunch of pollution-free solar, wind or nuclear plants, but let's assume the worst, and all that extra energy comes from coal. Per the EIA, every kWh generated by a coal plant produces two pounds of carbon dioxide. So 600 billion kWh x 2 lbs of CO2/kWh = 1.2 trillion pounds of CO2. Ouch.

Still, is that better than gasoline? The EIA says the U.S. consumed 3.3 billion barrels of gasoline in 2008, or 138 billion gallons. The Environmental Protection Agency says one gallon of gas belches out 20 pounds of CO2. That adds up to about 3 trillion pounds of CO2.


The Inevitable Conclusion

So if every car in the U.S. switched to electric, and every single watt of power for those vehicles came from a power plant that's coal-fired, we're still coming out ahead in the greenhouse-emissions game.

Sure, EVs won't work for all vehicles. Just highway travel alone poses a big problem. But the argument that you're just trading fossil fuels simply doesn't hold water. And that Chevy Volt is starting to look mighty good.