Are electric vehicles really any better for the environment than gas-guzzling cars?

Illuminating answers to environmental questions.
Dec. 11 2007 7:40 AM

The Electric Vehicle Acid Test

Are EVs really any better for the environment than gas-guzzling cars?

The Telsa Roadster. Click image to expand.
The Tesla Roadster

Would electric cars really be any better for the environment than our current gas guzzlers? So much of our electricity comes from coal, after all, which isn't exactly the cleanest source of energy. Might we all be better off simply upgrading to more fuel-efficient vehicles—that is, ditching our Hummers in favor of Toyota Corollas?

You're certainly correct in noting that an electric car isn't a zero-emissions vehicle. Driving one still has an environmental cost, mostly associated with the use of Santa's most feared stocking-stuffer: 49.7 percent of our nation's electricity is generated by the burning of coal. But if you break down the numbers, EVs still come out ahead of cars featuring internal combustion engines, especially in terms of carbon dioxide emissions.

Let's compare the Toyota compact to the forthcoming all-electric Tesla Roadster, which promises 245 miles' worth of travel per charge. The relatively fuel-efficient 2006 Corolla gets an average of 31 miles per gallon of gas, assuming it has a manual transmission. Over 100 miles, then, the Corolla will consume 3.23 gallons of gas, which in turn produces 63.11 pounds of carbon dioxide. (According to the Energy Information Administration, a gallon of gas produces 19.564 pounds of carbon dioxide—yes, seriously.) That figure, of course, doesn't include the energy expended to pump the oil out of the ground, ship it across the oceans, refine it, and get it to your local filling station.

Now let's look at the Roadster over that same distance. A recent analysis by Automotive Testing and Development Services found that for every 100 miles of travel, a Roadster needs to be recharged with 31 kilowatt hours of electricity. (Only about 70 percent of that charge goes toward creating motion; the rest is lost due to inefficiencies in the charging process.) Generating a kilowatt hour of electricity produces an average of 1.55 pounds of carbon dioxide, which means the Tesla vehicle emits 48.05 pounds of CO2 per 100 miles.

Your results will vary, though, according to your state of residence. In states that use the most coal, such as Wyoming, North Dakota, and West Virginia, the CO2 emissions per kilowatt hour are higher—so much higher, in fact, that the Roadster may emit just a few pounds less carbon than the Corolla when all's said and done. On the other hand, if you're a motorist in the Pacific Northwest, where hydroelectric power reigns, going with an EV is an even cleaner choice. (Use this nifty ZIP-code tool to determine how much of your electricity is coal-generated; the Lantern was surprised to learn that 49 percent of his own power supply comes from a nearby nuclear plant.)

Lower carbon dioxide emissions aren't the only advantage to going electric with your wheels. EVs such as the Roadster don't even have tailpipes, so there's not a constant plume of acrid smoke wafting into the air. As a result, EVs produce less methane, nitrous oxide, and assorted other greenhouse gases than their gas-powered counterparts. The one exception: sulfur dioxide, which is produced by coal combustion and can lead to acid rain.

The major shortcoming with EVs at present is the energy required to manufacture their enormous batteries. Some skeptics have contended that if you factor battery production into an electric car's environmental footprint, the vehicles really aren't that much greener than today's Corollas. But the Lantern finds studies such as this one too academic, since they assume that all of an electric car's "fuel" comes from coal; even in the heart of West Virginia, only about 73 percent of electricity is coal-generated. Also worth noting: a recent Department of Energy study pointing out that there's plenty of surplus electricity that goes unused at night, when people would presumably be recharging their cars.

One potential cause for concern is how EV batteries can be safely disposed of or recycled. Tesla states that its goal "is to include the cost of [battery] recycling in the purchase price of each car"—a price that currently stands at around $93,000 for the base-model Roadster, scheduled to debut next year. It's unclear, though, how much energy it will take to recycle the pricey vehicle's lithium battery.

Let's say the skeptics are right to some extent, though, and that EVs provide only marginal environmental benefits. Upgrades in power-plant technology, along with the creation of more alternative energy sources, would still make every EV cleaner. As green-car enthusiasts are so fond of saying, it's a lot easier to control emissions at a few power plants than at millions of tailpipes.

The real question, then, isn't whether EVs are environmentally superior to today's gas-powered cars, but how they stack up against another technological rival: plug-in hybrids. The Lantern promises to tackle that question soon.

Is there an environmental quandary that's been keeping you up at night? Send it to, and check this space every Tuesday.



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