It might help to know if your water heater is an Atwood or Suburban brand. These are usually the two models most people have.
If it is a Suburban, and you want to know if it can run on electric, open the access panel door outside your rig, and look to see if you have a small black rocker switch located in the lower left corner. It is often just slightly hidden by some of the propane tubing of the unit. You should also find a breaker inside the RV electrical panel identifying the circuit for the heater.
While you're in there, have a look around the perimeter and see if there is any labelling identifying what water heater model you have.
Ken and Terry
2010 Georgetown 330TS being pushed by our
2017 GMC Terrain toad (4 wheels down)