Generators are used in all significant A/C electrical power generation today except solar. It takes power to turn the stator of the generators, and the more power that is produced by the generator, the more mechanical power must be supplied to turn it. Most commercial generation systems use steam to provide the mechanical power to turn the stators. The steam is produced by heating water. This is frequently done by burning fossil fuels like coal and natural gas. Heat from nuclear fission is also being used to turn generator turbines as is water as hydroelectric generation. Another approach is use of generators driven by combustion engines, which is generally relegated to backup use in developed areas, but also in remote or less developed areas. These, of course, run on fossil fuels (diesel, gasoline, propane) .
In the ideal free energy or ZPE device, there are no moving parts, so in that way it is similar to solar power generation. In these, a direct current (DC) is produced that can then be converted to alternating (AC) current using the same inverter technology as used in the solar industry. There are also ZPE approaches wherein mechanical power is directly produced that can be used to power traditional generators. This could either be through heat to create steam or ZPE powered combustion engines or turbines.
Sometimes ZPE devices require some external power to operate, however the one necessary metric of a calling a device a “free energy” device is that it produces more power out that what is put in. We call this “over-unity production”.
A tenet of current physics is that one cannot get more energy out than what is put in, so many will not even entertain a discussion of the possibility of zero-point energy. Even with some credible demonstrations, the concept of free energy devices is problematic for most classical physicists and engineers to accept.
There are other interesting observed aspects to ZPE that have been reported, like devices becoming cooler as more power is extracted instead of hotter, and some devices losing weight or levitating.