today

The Honda FCX sounds for practical purposes a bit like the Toyota Prius, except that it runs on hydrogen, if you can find it. Ultracapacitators are used as a buffer between a fuel cell and the electric engine. This effect seems needed to allow bursts of high power from the fuel cells, rather sluggish otherwise. The key link may be the Ultracapacitators, which use carbon nanotubes to increase surface area, hence storage.

IMO: Too expensive FWIW- maybe £50,000. I'd stick with a Neva, at around 2 lacs in India, much more in UK but excellent value for money under London parking regulations, if a bit cramped.