Then it’s just heat transfer medium for most of geothermal powerplants too, because from what i understand, most of the time condensed water is recycled (and source of energy is just “hot rocks” anyway)

then if you look at the bigger picture, all that energy can be traced back to either sun, nuclear fission (in reactors) or nuclear decay/primordial heat (geothermal)

“Root” energy source really just depends on where you draw boundaries of thermodynamic system in question