Sad fact of reality in this dimension - there is no free anything, everything comes with a price. Nothing can be or will be 100% efficient.

There are no perpetual motions machines allowed in this dimension.

I read somewhere last year or maybe real early this year that somewhere in Japan they were powering homes with fuel cells - something about the size of a water heater/sm refrigerator. Su[pposed to run a house for a few months. No costs given, no discussion if it was for 12v DC system or inverted AC or any details. This is what its going to take - mass usage, mass production to make costs affordable. I'd hate to think what the fuel cells flying in the Shuttle cost.