Suburban rates the optional electric element on its Advantage tank water heaters at 1,440 watts. Run that off a battery bank and it pulls about 120 amps at 12 volts before the inverter takes its cut, and a 100Ah lithium battery, about 1,280 watt-hours, would be flat in under an hour. Off-grid, heat your water with propane. The element is a shore power feature.
Where the numbers come from
Suburban’s 6 gallon Advantage page lists a 12,000 BTU/h burner, a 1,440 watt optional element, and recovery of 10.1 gallons an hour on gas and 6.1 on the element alone. The product overview PDF gives the same element and the same 6.1 gallons an hour across the 4, 6, 10, 12 and 16 gallon tanks, with 16.2 gallons an hour on the 6 to 16 gallon models when gas and electric run together. Both read October 22, 2026. These are manufacturer ratings, not our measurements.
The arithmetic
Electric. 1,440 watts for an hour is 1,440 watt-hours, and it buys 6.1 gallons of recovery. That is about 236 watt-hours per gallon. A full 6 gallon tank at that rate is roughly an hour and 1,400 watt-hours. At 12 volts, 1,440 watts is 120 amps of DC, and inverter losses push that higher, not lower.
Propane. The EIA puts a gallon of propane at 91,452 Btu. 12,000 BTU an hour divided by 91,452 is about 0.13 gallons of propane per hour of burner time, for 10.1 gallons of recovery. A gallon of propane runs the burner about seven and a half hours.
Set those side by side. The same hour that costs you an eighth of a gallon of propane would cost you more than an entire 100Ah lithium battery on the element. Run a 1,400 Wh load through the solar calculator and look at the array it asks for.
The part that cuts the other way
The element is the more efficient heater. 12,000 BTU an hour is about 3.5 kilowatt-hours of fuel energy (EIA: 3,412 Btu per kilowatt-hour), and it buys 10.1 gallons, which is roughly 350 watt-hours of input per gallon against the element’s 236. The burner loses heat up the flue and the element does not. That matters when the electricity is a campground pedestal you have already paid for. It does not matter when the electricity came out of your battery.
Suburban does not state the temperature rise behind its recovery figures on the pages we read, so use these numbers to compare gas with electric, not to predict how hot your shower gets.
What to do
- Boondocking: leave the element switch off and use gas. On the DEL models Suburban says the inside switch “powers the electric element circuit.” If your inverter feeds that circuit, the switch is all that stands between your battery and a 1,440 watt load.
- On a generator: 1,440 watts is a continuous load, and it stacks on whatever else is running. Add it in generator sizing before you assume a small inverter generator will carry it alongside the microwave.
- On shore power: run both if you want speed. 16.2 gallons an hour is the fastest recovery the tank offers, and the element half of it is coming off the pedestal.
The same trap shows up with an 1,800 watt induction burner, and the fix is the same: budget in watt-hours, not watts. Our power budget guide is where to start.
Sources
- Suburban Advantage 6 Gallon Tank Water Heater specifications (12,000 BTU/h, 1,440 W element, 6.1 and 10.1 GPH recovery)
- Suburban Porcelain Lined Steel Tank Water Heater Product Overview (model table and recovery rates, 4 to 16 gallons)
- U.S. Energy Information Administration, British thermal units (Btu) conversions