[olddog]

I believe diesel operates at the lowest $/Kwh rate. A large fuel tank, not so handy as a Ng line.

Look at the newer better generators that back down to an idle at light loads. I believe these use an AC inverter to continuously give out a 220 volt 60 Hz power regardless the engine speed. I have not dug into the details of how they work, so there are assumptions in what I believe.

The old syle generators require an exact engine rpm to get 60 Hz. Engine RPM affects voltage and the load affects the voltage. At light loads the voltage floats higher. Engine governors are generally a spring pulling against a wind flap or a centrifugal weight system. Therefore they are a proportion only controller, with no integral to trim the rpm to the set point. This mean there is only one load level that the voltage and Hz is dead on the money. So voltage can go high enough to cause plug in surge (voltage spike) protectors to trigger. Since the problem is not a short spike, but a continuous condition, these surge protectors can overheat and catch fire. I have done it. My father has done it. I know dozens more who have had it happen. Stay away from cheap stand alone generators. Trust me on this point.