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
2018 Sunseeker 2430S-CD, nicely modified and carried by a 2017 Ford E450 Sport
Former Georgetown 330TS owner for 10 years with more mods than I can count