It's official: The Nissan Leaf electric vehicle gets the equivalent of 99 mpg in combined city and highway driving.

The Environmental Protection Agency has approved the window sticker you'll see (.jpg) when the Nissan Leaf rolls into showrooms next month, and it says in big bold letters, "99 MPG equivalent combined 106 city, 92 highway."

How'd they arrive at those figures? According to Nissan, the calculation is based on the EPA's formula of 33.7 kilowatt-hours being the equivalent of one gallon of gasoline. The Leaf's 24 kilowatt-hour pack is good for a driving range of 73 miles. The window sticker says the car charges in seven hours at 240 volts.

Nissan has said the Leaf will deliver a range of 100 miles based on the LA4 driving cycle. Further muddying the waters, the Leaf also will feature a sticker from the Federal Trade Commission, which regulates advertising of alt-fuel vehicles, stating the car has a range of 96 to 110 miles, according to The New York Times.

The question of range is dependent upon several factors, including driving style and ambient temperature. Drive like Formula 1 champ Sebastian Vettel on a blistering hot day with the A/C cranked and you'll get far less range than if you drive like grandma on a pleasant day. That's why Nissan says drivers will experience "a range of ranges."

“We're trying to be very open so folks are making the right decision for them," Mark Perry, Nissan's director of EV and advanced technology strategy, told The Times. "We don’t want them to be surprised."

The EPA says annual electricity costs for the Leaf will be $561.

Photo of the Leaf on the assembly line: Nissan