If our system is the only generator on board, there will be times when a propulsion engine has to be run at anchor, in neutral, to generate electrical energy. This is a worst-case scenario because we potentially have a serious mismatch between the rated power of the engine and the rated output of the generating device. However, we have designed the device such that its output ramps up very rapidly from engine idle speeds. For example, by the time an engine is up to 1,000 rpm (a little above idle speeds for most engines), generator output is up to 5 kW. This is enough of a load at these low engine speeds to lift even a fairly powerful engine out of its chronically inefficient, low-load region of operation. We then maintain excellent engine efficiencies by operating the engine at variable speeds, depending on the electrical load. We have found in extensive testing that generating efficiency is as good as the peak efficiency of almost all stand-alone AC generators, and is considerably better than the average efficiency of these generators.