What Size Generator Do You Need for an Electric Water Heater?
An electric water heater draws about 4,500 watts on a 240-volt circuit whenever its elements are on. It needs a large portable or a standby generator, and it's usually the first load to leave off the backup list.
| Appliance | Running / starting W | On its own | With fridge, lights and Wi-Fi |
|---|---|---|---|
| Electric water heater | 4,500 / 4,500 | 7,500-watt 10 kW standby | 8,000-watt 10 kW standby |
Smallest portable (by starting watts) and smallest standby generator on natural gas, keeping about 20% headroom.
Tips
- A full tank stays hot for a day or more if you don't run it; most people switch it off during outages.
- If you do want hot water, heat it in short bursts while other big loads are off.
See also the appliance wattage chart and what each generator size can run.