Works in conjunction with the gas for quicker recovery. Our WH has the motor aid, gas and electric. When on the road the water is heated as we drive by the engine coolant. When we have full hookups I just use the electric element unless we need quick recovery (showers of wash a load or two), then I run both.
Also, be careful when using the electricity. If you turn the element on and there's no or not enough water in the tank you'll burn the element out in just a very short time, like 30 seconds, maybe less.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '14 Jeep JKU Dragon Edition