True, but in this case we are storing the best form of energy, electricity as opposed to a car engine. You might need cheaper electricity to make this gadget more than a marginal improvement over what we're stuck with now.
20% is also about the efficiency of an ICE, which is also "a bit painful", but we use them anyway. Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
