[FredF]

Yes the outside switch is for electric operation of the water heater. It will heat the water up to the setpoint and will attempt to keep it there with water usage. If you have shore power ( or generator ) you can save you propane and only run on electric. On the other hand if you have no electric connection and want hot water you need to use the switch on the control panel to turn the propane burner on. If this switch is off, the burner will not come on regardless of the water temperature. You can also use both if you want lots of hot water (relatively) fast. Remember to turn the electric switch ( outside ) to off before you empty the water tank - something you need to do to winterize. If you leave the switch on with ne water in the tank, as I have done, and plug the unit in over the winter to keep the battery charged it will destroy the electric element.