For the duration of a thirty-six month lease, starting next spring.
We know that hydrogen fuel cell vehicles have technically been around for years, but these have thus far been experimental vehicles, purposely produced in small numbers and at great expense to the manufacturer. So the race to bring out a proper mass market hydrogen vehicle has very much been on. And it now looks like Hyundai will be the first to the market, with the 2015 Tucson Fuel Cell set to hit showrooms next spring.
Of course, the words "mass market" might be a bit ambitious. Since California is the only state with any real hydrogen infrastructure to speak of, the car will only be sold there, and actually only at four dealerships. But Hyundai will build as many as they can unload, and will expand the dealer network as the fuel becomes available, so that's already more mass market than any previous hydrogen car. There is also the issue of whether you'll actually be able to buy one. Hyundai has so far only released information about leasing the car, so it's unlikely you'll be able to buy the car outright.
Since the price would likely be affected by various tax incentives and so forth, it's possible that Hyundai simply haven't commented on it yet, and a price is in the works. The lease will set you back $2,999 down, and $499 a month after that for 36 months. But that's actually a better deal than it sounds, as it also comes with free unlimited fuel for the length of the lease. The car has all the advantages of an EV, with the added benefit of a 300-mile range and a refueling time comparable to that of a gasoline-powered car.