HAWTHORNE, Calif. – Tesla Motors is doubling down on its commitment to offer fast charging for its electric Model S models.

CEO Elon Musk announced that Tesla will offer the ability to swap a depleted battery for a fresh one in as little as 90 seconds.

To demonstrate the point, Musk threw a party at Tesla design center here and showed how two electric sedans could get a battery switch in less time than it took for a conventional car to get a 20-gallon fill-up. The model is rated at up to 265 miles of all-electric driving.

Musk says the automated quick-change battery stations will be installed alongside the company’s fast chargers. The first ones will go along major highways between population centers, like the Boston to Washington, D.C., run.

Supercharging, designed to quickly refill batteries with juice while drivers get a meal at a nearby restaurant, will remain free. Musk says the ability to get a fresh battery in as little as 90 seconds will incur a charge pegged to the price of about 15 gallons of gas.

Tesla’s swoopy electric sedan had been designed with battery changes in mind all along. There was just no way to exploit the capability.

Musk says battery swapping helps to put electric cars on the same footing as gasoline cars.