Hey Mr. Green,
The cover story in Sierra asks, “Can we really get off oil in 20 years?” As long as Mr. Green claims “EVs can be responsible for releasing almost as much CO2 as a 40-mpg car” the answer will be “of course not.” The Nissan Leaf, not unlike EV conversions driven for years, has a 99 miles-per-gallon-equivalent EPA rating. Further, the same amount of gasoline used to power a combustion vehicle, if burned in a conventional power plant, can put six electric vehicles (EVs) on the road.
--Bob, Grants Pass, Oregon
Don’t get me wrong. EVs are greener than conventional cars, but beware of naive enthusiasm about the environmental blessings of EVs. An EV is only as clean as the source of its electric power, and even if it runs on 100 percent clean energy, the EV can do little to ease a host of environmental problems caused by an ever-increasing number of cars, regardless of their power supply.
The way this “equivalent” mpg rating gets presented is itself an example of the overly rosy view of EVs. The mpg rating you cite is misleading, if not downright deceptive, because it is correct only if the EV derives all its electricity from sources that don’t use fossil fuel to create electric power. Yes, the Nissan Leaf does travel 99 miles on the equivalent of the energy in a gallon of gasoline, or about 115,000 British thermal units, or 33.7 kilowatt hours of electric power. But these numbers do not reflect the large amount of additional energy required if fossil fuel is burned to generate that electrical power. This “hidden” energy isn’t reflected in the 99-mpg number.
The reason is that when its electricity is generated by fossil fuel, the EV is, in effect, being powered by fossil fuel, not by some morally superior electricity from a virginal source. When fossil fuels generate the EV’s electricity, there is a loss of energy, because fossil-fuel-powered dynamos are typically 35 or 40 percent efficient. This means that the electrical energy an EV uses from the fossil-fuel-powered plant equals only 35 or 40 percent of the fuel energy burned in the plant. Therefore it could actually take as much as 10,000 Btus to create your kilowatt hour of electricity (3414 Btus), meaning that in reality your Leaf needs the equivalent of around 335,000 Btus for its electricity, or the energy contained not in one gallon of gas, but in 2.9 gallons. So in real fossil-fuel-energy equivalents, the Leaf gets around 35 miles per gallon. This makes it obvious that burning the gasoline used by one conventional car in a power plant couldn’t possibly power six EVs, unless they were micro-vehicles with passengers of considerably less heft than our current population.
Still, EVs beat conventional cars because 1) it’s easier to control pollution from a few thousand power plants than from 250 million vehicles 2) EVs don’t require motor oil, or ooze out other toxic fluids, and 3) EVs can be powered by clean sources of energy, though it will be years before such energy is widely available.
Like all environmentalists, I’d love to see the world “get off oil” and other fossil fuels because of the immense damage caused by extracting them (e.g., mountaintop mining, oil spills), not to mention the homicidal depravity and insane waste of fighting wars to secure petroleum. But let’s not make a fetish of EV technology, as has been our habit in bowing down before technological miracles” that turned out to have some dicey unintended consequences.
Many of same old problems caused by our irrational dependence on automobile transportation would persist even if all cars were EVs rolling over the asphalt and concrete on “clean” energy. We're driving 105 million more vehicles on 200,000 more miles of roads than 35 years ago, on a paved area that already exceeds 60,000 square miles, 7,500 of which are dedicated just to parking, according to the federal government and the Environmental Policy Institute). Nor are EVs likely to diminish the immense personal grief and public-health problems caused by highway fatalities and injuries. Moreover, even clean energy doesn’t come without an environmental price to pay in building power lines and siting windmills and solar installations on the land. For all these reasons, if EVs end up encouraging more driving by giving a green dispensation to cars, they could turn out to be a dubious blessing.