I cruised thru the thread. To have a propulsion system that doesn't make any noise is one thing. To go that route & then buy a diesel generator to recharge the batteries.....
Maybe it's just me but I have trouble wrapping my head around that one.
The idea is basically that you can propel at any time silently and you can later choose the time and place to make your noise.
I don't do a lot of motor-sailing because for me, once I fire up the (very loud) Perkins diesel, I figure I may as well go 6knots with it. The diesel likes the load and is most efficient on fuel at 80% of hull speed so when the sailing gets slow I take it all down and fire up the diesel.
If I had electric I could take 3knots of sailing speed and increase it silently to 5 or 6 knots without having to start up the motor, without the noise, without waiting for it to warm up, without disturbing the crew below etc etc. Later I could run the diesel to top up the batteries. In fact, the hour of maneuvering into the anchorage and setting the anchor would go a long way towards the amps used in increasing your speed under sail.
It's really not an efficiency thing, it's a peace and quiet thing and about enhancing your ability to sail. After all, if I wanted efficiency instead of peace and quiet out on the water I would have a power boat, or take the ferry.... Sailing itself is not efficient by cost, time, or any other measure....
Does that help?