Proof is in the pudding. Let’s see a prototype of any kind that actually outputs more energy than went in. We can go from there.
There have been more than a dozen such prototypes. Some have had Coefficient of Performance [COP] Output/Input of infinity when they were in “heat after death” mode.
My favorite was Dr. Schwarz’s NANOR device which ran for several MONTHS at MIT with varying COPs between 9 and 2000.