BMW is preparing for a future that isn’t entirely battery-powered.

The German luxury marque has just unveiled a new flat tank system for the hydrogen-powered iX5. The revised design increases tank capacity, pushing the SUV’s range to well over 350 miles.

It may seem like BMW has focused most of its attention on its next generation of “Neue Klasse” EVs, but the company has actually been working on a hydrogen-powered alternative since 2022. The vehicle, which is based on the mid-size iX5, features a futuristic propulsion system developed in collaboration with Toyota that includes electric motors and a hydrogen fuel cell. The idea has been to create an ultra-efficient system that produces zero emissions and can be refueled quickly.

That vehicle, when it does finally arrive, will feature BMW’s aptly named Hydrogen Flat Storage System. The setup features seven high-pressure tanks reinforced with carbon-fiber composite, connected in parallel, and integrated into the frame of the vehicle. The new configuration, in which the tanks are interconnected as opposed to separate, boosts total hydrogen capacity to at least seven kilograms, whereas the current concept maxes out at just six kilograms. Because of this, the driving range is boosted to roughly 385 miles, an increase of 85 miles. Refueling from empty, meanwhile, takes just five minutes, which is just a fraction of the amount of time it takes to recharge an EV, even one with fast-charging capabilities.

The new flat tank system isn’t just more efficient than the previous hydrogen fuel system; it also takes up less space. BMW says the setup fits into a metal enclosure that is the same size as the one that holds the battery in the standard iX5 without protruding into the cabin of the vehicle.

“Our new storage concept allows us to fit the hydrogen drive system into the new X5 precisely and in a way that saves space,” Joachim Post, member of BMW’s Board of Management, said in a statement. “Think of it as installation Tetris: every customer gets the drive system best suited to their needs and a true BMW X5 with no compromises.”

Although a firm sales date has yet to be set, BMW continues to say the iX5 Hydrogen will arrive in 2028. If the company is able to stick to this time table, that means that customers will likely be able to buy an X5 with their powertrain of choice—pure gas power, hybrid, battery electric, and hydrogen—by decade’s end.