Do you have a compartment door inside that permits access to your HWT? Our AC on/off switch is in there on the tank (along with the HWT bypass valves used for winterizing).
Another check to see even if you have an electric heater in the tank is to look for a circuit breaker for it in your breaker box. If you don't find a breaker, your HWT is, most likely, propane only.
2009 GMC Sierra 2500HD | Crew Cab | Standard Box | 4WD | Duramax/Allison
2000 Jayco Eagle 266 | FBS | TT
1986 Coleman Laramie pop-up -- Still in the family!!!