A lot of people say perpetual energy, but what they probably mean is energy that replenishes itself from an unknown force. There was an indian dude who meditated himself to not need food. scientists examined his belly and found food particles breaking and reforming without explanation. Nifty. Energy could do this in the right way.
10 watts of power can only to 10 watts of force. But if it is replenished by an exotic machine it can do massive things.
For example, the moray device, resonates and entrains with cosmic rays, background radiation, to generate electricity. Seems to come from nothing, but it actually is resonation and entrainment energy. it was hated because people didn't understand it. Today's scientists still don't understand a lot of this kind of thing.