Think of it as an electric car that you fill with hydrogen when it gets low, so it's an electric car without the range limitations. It's pretty good now, and it's still a development generation from production.

It might still be five years from production, but BMW's first production fuel-cell electric car will be big. Very big.

BMW plans to bring a large, i-badged hydrogen fuel-cell electric car into its showrooms by 2020.

The BMW board itself is still unsure whether it will be dubbed i6 or i7, but it will definitely be a large, five-seat luxury sports saloon capable of more than 500km of pure electric running for each tank.

It will fill up with liquid hydrogen, stored in a pressurized, cryogenic tank running down the middle of the car, in a slightly larger space than a transmission tunnel currently uses to drive the rear wheels.