What size generator to run an electric water heater?
Electric water heater sizing at a glance: it draws 4000 running watts.
| Spec | Value |
|---|---|
| Running watts | 4000W |
| Starting (surge) watts | 4000W |
| Recommended class (this load + margin) | 5000W |
Why the startup surge matters
A electric water heater is a resistive load, so it has no meaningful startup surge. If you size a generator only for the running watts, it can stall the instant the electric water heater switches on. Always size for the surge.
Sizing the whole system
The number above covers the electric water heater on its own with a safety margin. In a real outage you'll run other things too — and the right method is your total running load plus the single largest surge among everything, not the sum of every surge. Use the full calculator to size your actual setup:
Common questions
How many watts does an electric water heater use?
A typical electric water heater draws about 4000 watts, with no significant startup surge.
What size generator runs an electric water heater?
For the electric water heater alone plus a safety margin, a 5000W (≈5.0kW) class generator is appropriate. Add your other essential loads to size the full system.