The EPA has come out with its fuel economy ratings for the Nissan Leaf electric sedan, which goes on sale in December in 5 states. EPA labeled the car the best in its class in terms of fuel economy, using the EPAs formula that says that 33.7 kilowatt hours is equivalent to a gallon of gasoline, according to Nissan. By this measure, the car gets the equivalent of 99 miles per gallon (although it doesn’t use any gasoline, just power from the grid).

But while the car is designed for a 100-mile range, it actually only gets 73 miles under drive tests meant to simulate real-world driving. Nissan has said before that mileage would vary, but gave the impression that 100 miles was the normal case, and the one sanctioned by the EPA (its website says the EPA LA4 cycle puts the range at 100).

According to Nissan, under some driving conditions, such as sitting in traffic with the heat blasting, the car will only go 62 miles on a charge. Traffic jams that keep you on the road longer than 4 hours will leave you stranded. Nissan gives a range of scenarios for driving range, but none of them include driving at normal highway speeds of 65 to 70 miles per hour, which in combination with the stereo blaring and the heater cranked might lower the range below 62 miles.

File under: caveat emptor.