Our water heater (propane only) is turned on before we leave for a trip and turned off when we get home. For about 70 nights a year camping, we use about $25-30 a year, for hot water, cooking, furnace the odd time, and fridge on when traveling.
We have been relaxing near the RV, we have heard the water heater (NO hot water usage) cycle on periodically, maybe ever every 2 hrs or so. and then it is only on for less than 2 minutes.
That said, its a very small cost for the convenience (forget to turn on be use).
Beverley and Ken