With my factory installed fireplace I have to toggle a switch which alternates between fireplace OR water heater (elec. or propane). The point is to keep in mind your total current draw.
Last Nov. I found out that my elec. space heater (+ hot water) and the microwave don't agree with each other.
2008 Jayco Eagle SuperLite 29.5
2014 F250 6.7 PSD 4X4, CC LB