I just noticed today that our EH-101 has 3 generators (one for each engine), but we only have switches for turning two of them on and off... thus you can never turn off the third one, which means that as long as that third engine is running, the electrical systems in the cockpit keep running!
To change the number of generators for an aircraft, you can use the engine_generator_map parameter in the [electrical] section of your aircraft.cfg. For example, in the EH-101, this should be:
This indicates that there should be a generator driven by engine one, a generator driven by engine 2, but no generator driven by engine 3. Likewise, in a 4-engine aircraft, "0, 1, 0, 1" would indicate 2 generators attached to engines 2 and 4.
Just thought I'd share in case it helps someone else! This is documented in the SDK, but it's easy to miss and I thought the explanation was a little too brief. :)