Is the electric option factory? Or is it one of the aftermarket add-ons with the element screwed into the drain port? The after market kits draw about a third of the watts that the factory electric element uses, and heat up the water much slower. A lot of folks use propane for the initial heating with those, and then let the electric element maintain the temperature. The factory element will normally heat up the water about as fast as the propane side. For fastest heat up or recovery though, use both at the same time.