A fully reversible computers would consume no power whatsoever, so wouldn't require power to function. Instead, you would need power to (re)initialize its state

A fully reversible computers would consume no power whatsoever, so wouldn't require power to function. Instead, you would need power to (re)initialize its state, or to copy the results of its computations to e.g. your monitor. An unplugged reversible computer would be free to compute (and uncompute) its bits perpetually, unconcerned about the rest of the world. The functional programmer's dream, in a sense.