If the AC switch is on (and breaker) then the water heater element is on. If the switch for the propane is on then the gas side of the water heater is also on.
If you want to use electric only then turn the switch for the propane off.
Some people have both on. This gives them the ability to maintain their hot water using electric and a fast turnaround when hot water is demanded using propane. I personally just have my electric on and the propane off in my seasonal site.
Todd & Sheila and kids
2012 Surveyor SV-305
2012 Dodge Ram 1500 4X4 CC Outdoorsman