“Energy conversion over lifetime doesn’t look good for an engine that’s hardly ever used.”
We were discussing engine life, not energy conversion.
We were discussing the whole ridiculous picture. You continued to defend the ridiculous configuration. Without any use at all, the engine will need periodic fluids maintenance, and will develop problems after some number of years not an order of magnitude away from 20.
There’s probably an optimal on / off cycle for maximum engine life. That life will be longer than some normal to high number of miles driven in some conditions per time. So the engine can last longer with light use charging a battery. How much longer? How many enging problems have nothing to do with high mileage? In my experience, a significant number.
But we are off track here. You don’t see the facial foolishness of this rig. That is ok with me, but since you won’t budge, we’re done.
You asked what is optimal. I gave one example relating to a gasoline engine. Don’t just be a jerk, if you can help it.