by the way the COP=6 is first conservative, but the need is not of electricity but of heat... of course today he use electricity because it is easy to control. in fact it seems that hyperion, and maybe soon e-cat will self sustain quite long. also as said here, if you can produce electricity, juste recycle your own heat or electricity, and maybe even cherge an accumulator to be able to start from cold, like a car...
COP is a non-sense for a really producing device... efficiency (usable energy/(energy produced+consumed)) is more rational to use...
