When I see electrical generators specified, they usually give the fuel consumption as at "rated load". So,for example, a 5 kilowatt generator might consume 0.6 gallons per hour.
However, what happens if the load is less than 5 kilowatts? Does the generator still run at the fixed rate and any excess electricity is just shorted to ground?
Or does the engine run slower and just generator less energy? How does it know what rate to run at? Does it have to manually adjusted?
If the engine is run at less than its maximum load, what would be a typical loss of efficiency? Can someone provide an example curve that shows how a generator loses efficiency at sub-optimal loads?