I am surprise it only takes about 1 KWH for a launch, that's the equivalent of 1/10 of a liter of gasoline, using the conversion number you gave above.

Our winch uses on average 1 cup of gas (~240cc) per launch. The engine is a 7.5l V8 with a carburetor. Going to fuel injection would lower that consumption but we would have to do a lot of launching, before we recover that investment.
There is a very promising electric winch project on the way in the US. Stay tuned for news in the near future...

Uli
'AS'