WASHINGTON — The Nissan Leaf, an electric car aimed at attracting environmentally conscious motorists, will get the equivalent of 99 miles per gallon of gasoline in combined city and highway driving, based on government testing. Nissan Motor Corp. said Monday the Environmental Protection Agency’s fuel efficiency window sticker, which provides information about the car’s energy use, would estimate the electric car will achieve the equivalent of 106 mpg in city driving and 92 mpg on the highway. EPA’s tests estimate the Leaf can travel 73 miles on a fully charged battery and will cost US$561 a year in electricity. Nissan has said the Leaf can travel 100 miles on a full charge, based on tests used by California regulators. Both Nissan and General Motors Co. are releasing electric cars within weeks in the auto industry’s most prominent attempt at mass-producing vehicles that shift away from petroleum. The Leaf does not have a gas engine and must be recharged once its battery is depleted. But the tests show equivalent fuel efficiency of nearly twice the Toyota Prius, which gets 50 mpg in combined driving. GM’s entry, the Chevrolet Volt, uses an electric battery for the first 25 to 50 miles and a small gasoline tank to create an additional charge for another 300 miles. GM has not yet revealed the mileage rating for the Volt. Mark Perry, Nissan North America’s director of product planning and strategy, said the vehicle’s range would vary based on driving conditions. Tests conducted by the Federal Trade Commission, which regulates advertising claims, had estimated a range of 96 to 110 miles per full charge and the company’s internal tests had found a broader range of 64 to 138 miles, Perry said. The California Air Resources Board estimated a range of 100 miles. “As we’ve said all along, your range varies on driving conditions, temperature, terrain and we’ve talked about, very openly, this idea of a range of ranges,” Perry said in an interview. The Leaf’s label will indicate the vehicle is the best in class in fuel efficiency and tailpipe emissions. Nissan will start selling the Leaf in California, Washington, Oregon, Arizona and Tennessee in December with a sticker price of US$32,780. The Leaf will go on sale in other markets through 2011 and be available nationwide by the end of next year.