Electric tank water heaters draw thousands of watts, far beyond most batteries. See why, what your tank holds, and practical hot water options.
- Electric tank heaters use thousands of watts, usually on 240 volts.
- A well insulated tank stays warm for a good while, so use it sparingly.
- Spend battery power on essentials, not on heating water.
People often ask whether a power station can run a hot water heater. For a standard electric tank heater, the honest answer is no. These appliances are among the biggest electrical loads in a home, and a portable battery is simply the wrong tool for the job. The good news is that you probably have more hot water on hand than you think, and there are easy ways to make it last.
How many watts a tank heater uses
A typical household electric tank heater has heating elements that draw several thousand watts when they are on. The label on the tank will list the element wattage and the voltage. Most are wired to a 240 volt circuit in North America, which many portable power stations cannot supply at all, since they output 120 volts.
That combination of high wattage and 240 volt wiring is why a tank heater is out of reach for almost every portable unit. Even a very large battery would be drained in a short time. Heating water takes a lot of energy, and a battery is a poor way to store heat compared with the tank itself.
What your tank keeps hot for you
A tank water heater is an insulated storage vessel. When the power goes out, the water already in it stays warm for a good while, and it cools slowly. A tank holds a large volume, commonly in the range of 150 to 270 litres (40 to 70 gallons), though yours may differ. Check the label.
- Do not open hot taps more than needed. Every draw pulls cooler water in behind it.
- Take short showers or sponge washes rather than long baths.
- Use the hot water for dishes and washing in one batch.
The tank can also be an emergency water source. If the household supply is disrupted, water in the tank is usually safe to drink after it cools, if you drain it from the bottom valve. Turn off the power supply and the water supply to the tank first, and check your manual or official guidance. See how much water to store for planning numbers.
Why not just wire it to a generator?
Some homeowners connect a large generator through a properly installed transfer switch, which a licensed electrician must set up. This can include a water heater circuit, but it adds a big load. Many people choose to leave it off the generator circuit and accept lukewarm water for a few days. Our guides on what size generator do I need and transfer switch vs extension cords explain how to size and connect safely. Generators must only run outdoors, well away from windows, doors and vents.
Practical alternatives for hot water
- Use what is in the tank first, using it sparingly.
- Heat small pots of water on a safe stove. Gas stoves vary by model, and a camp stove must only be used outdoors. See how to use a camp stove safely.
- Use a thermos or insulated bottles to hold hot water for washing and drinks.
- Switch to sponge baths, and use a washcloth with a small basin.
- For long outages, think about a solar shower bag in summer, which needs no power at all.
Gas and heat pump heaters
Gas tank heaters still need power for controls or ignition on many models, so they can stop working in an outage even though they burn gas. Heat pump water heaters use less power than resistance models but are still a significant load, and often a 240 volt one. Check the manual for what your model needs.
What to do instead of powering the heater
Spend your battery on the things it does well: a fridge, lights, phone charging, a router, and medical devices. Our how many watts to run a house guide shows how quickly big loads add up, and the power station hub can help you choose a unit sized for essentials rather than for the whole home.
Quick answers
Can a portable power station run an electric water heater?
Almost never. The wattage is very high and most portable units output only 120 volts, so they cannot run a standard tank heater.
How long does a water heater stay hot without power?
It depends on tank size, insulation and room temperature, but a full insulated tank cools slowly and stays usable for a good while if you avoid heavy draws.
Is the water in my water heater safe to drink?
Usually yes once cooled, if drawn from the drain valve after shutting off power and water. Follow your manual and official guidance.