At the LA Auto Show today, Audi unveiled the A7 Sportback h-tron quattro, a modified version of its swoopy four-door coupe that swaps out the traditional drivetrain for a hydrogen fuel cell and electric motors at the front and rear. It'll go over 300 miles between refuelings, which take three minutes — a far cry from the hours that it can take to fully recharge a battery-powered electric vehicle. The h-tron is also a plug-in hybrid, which means you can connect it to charge a battery with roughly 31 miles of range.

It's just a proof of concept — for now

California is becoming a popular place to announce hydrogen cars: Honda actually already offers one for lease here, the FCX Clarity, and has announced another (the FCV Concept) for 2016 release. Toyota, meanwhile, is using California as its launchpad for the Mirai sedan. A major reason for that is infrastructure: hydrogen cars require hydrogen stations, which don't exist in sustainable numbers at this point. Toyota is working with California to build out a network there, and has also announced a partnership in the US Northeast to do the same. Globally, though, the cars don't do much good until the stations are widespread.

There's no indication that Audi plans to sell the A7 h-tron — it's billed as a technology demonstrator, just as many of Audi's e-tron EVs have been — but the company says it can make hydrogen cars should the stations ever actually exist. "The h‑tron concept car shows that we have also mastered fuel cell technology. We are in a position to launch the production process as soon as the market and infrastructure are ready," says Ulrich Hackenberg, who leads technical development at Audi.