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Electric Cars: How Green Are They Really?

Last Updated Jul 21, 2010 1:40 PM EDT

Electric cars are speeding toward their broad U.S. introduction late this fall, but are they really as green as you think?

Nissan has 19,000 orders for its all-electric Leaf and expects to hit its limit of 25,000 shortly. Chevrolet's Volt, battery-powered with an auxiliary gasoline generator, recently expanded its initial ordering locations for 10,000 cars to include Austin, Texas and the New York City area. And states from Washington to Maryland are installing public charging stations. Ford plans to sell an electric Focus next year, Honda will bring an electric car to market in 2012 and BMW's electric sedan will go on sale in 2013.

But an important debate has sprung up: How green are plug-in electrics like the Leaf (pictured here) when the power plants generating their charge may be fueled by coal or other polluting fuels?

The short answer: It depends where you live and how power is generated there (see details below).

Electrics may also not be quite as green as originally thought in gas mileage terms. Manufacturers have lowered their initial, very high estimates of the gas mileage equivalent for plug-in vehicles. Chevrolet initially said it expected the Volt to get a rating equivalent of 230 mpg. But now the company is projecting lower numbers--though not yet specific--after a change of methodology. That calculation is decided upon by the Environmental Protection Agency as part of their mileage rating program. The EPA is still working on its final guidelines, which may not be ready until just before the new electric models' release in November. Some scientists say an mpg rating makes sense only for when the gasoline engine in the Volt (pictured at right) is actually running. For battery power in the Volt or the all-electric Leaf, the argument goes, a kilowatt-per-mile electric usage rate makes more sense.

Auto makers' eagerness to sell electric cars is prompted partly by a new federal requirement that overall, each company's cars must average 35.5 mpg by 2016 (see Hybrids, Electric Cars and More: What You'll be Driving in 2016). Though the environmental impact of a plug-in electric will vary with location, the green machines have some clear advantages over standard vehicles. Because of their greater efficiency, plug-in electrics are responsible for about 30% fewer climate-changing greenhouse gases than conventional gasoline-powered cars, even if the electric vehicle is charged with a coal-fired power plant, according to a joint study by the Natural Resources Defense Council environmental group and the utility industry-sponsored Electric Power Research Institute.

If you want to calculate the environmental and financial impact of a personal decision to go electric (see Should You Buy an Electric Car?) take these steps:

For climate impact, check your power source. Indiana and Kentucky, for example, get at least 90% of their electricity from heavily-polluting coal plants. But California, one state where the Leaf and Volt will be sold initially, has reduced its coal generating to 1% of the total power generated , with 48% of that power in low-emission natural gas and the balance from no-emission hydroelectric, nuclear, wind and solar generation. To see the power plant balance in your area, go to the web site of Get Energy Active and click on your home state.

Check what charging will cost. Research the off-peak rates your local utility charges when usage is low. To take advantage of those rates, you won't have to wake up late at night to plug in the car. So-called "smart charging" can program the vehicle to charge at those off-peak hours. Ford just announced a joint venture with Microsoft for a smart charging system, and others are in the works. An electric vehicle used to commute probably will need to be charged daily. (Leaf can go a purported 100 miles before recharge, the Volt 40 miles). With a home charging station sold by Nissan with the Leaf and costing $2,200, a full recharge will take about eight hours.

Investigate the tax credits and bennies. With the Leaf priced at $32,780 and the Volt expected to be over $40,000, any possible savings will help. So you'll want to take advantage of the federal government's $7,500 tax credit for these cars and other electrics. Some states give you an additional tax credit (in Georgia, it's the lesser of 20 percent of the vehicle price or $5,000). Additional perks where you live might include special parking spots and use of high-occupancy highway lanes even with no passengers.To see both state tax credits and benefits for your home state, go to the web site of The Car Electric.
Photos courtesy of the manufacturers

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