How many watts does an electric water heater use?
An electric water heater draws 4,500–5,500 watts while running, which is 18.8–22.9 amps on a 240 V circuit.
Electric water heater watts, amps and circuit
| Running watts | 4,500–5,500 W |
|---|---|
| Voltage | 240 V |
| Running amps | 18.8–22.9 A |
| Circuit | 30 A breaker, dedicated circuit |
| Wire size (copper, NM-B cable) | 10 AWG |
Also called: water heater, electric tank water heater, 50 gallon water heater, 40 gallon water heater.
Electric water heater watts by size and type
| Size or type | Running watts, W | Volts, V | Amps, A | Starting watts, W |
|---|---|---|---|---|
| Electric water heater | 4,500–5,500 | 240 | 18.8–22.9 | — |
| 4,500 W elements | 4,500 | 240 | 18.8 | — |
| 5,500 W elements | 5,500 | 240 | 22.9 | — |
What size generator runs an electric water heater?
An electric water heater needs a generator that supplies at least 5,500 running watts. A 7,500 W generator covers it with its running rating alone; add the watts of anything else you run at the same time. The generator must have a 240 V outlet or be connected through a transfer switch or interlock.
What it costs to run an electric water heater
Running an electric water heater at 5,000 W, the middle of its 4,500–5,500 W range, for one hour a day uses 1,825 kWh a year. That costs about $329 a year at $0.18 per kWh, the US average residential price for August 2026.
Your bill's total ÷ kWh used. 0.18 is the US residential average.
- Per day
- $0.90
- Per year
- $329
- Energy per day
- 5 kWh
- Energy per month
- 152.1 kWh
How it is calculated
- kWh per day = 5,000 W × 1 h ÷ 1,000 = 5
- Per month = 5 kWh × 30.4 days × $0.18 = $27
What affects electric water heater power use
A tank water heater has two heating elements wired so that only one heats at a time, so it draws the rating of one element. Tank size does not set the watts; the element rating on the label does. GE lists a dedicated circuit of at least 30 A for its 5,500 W model, and how long the heater runs depends on how much hot water the home uses.
How the amps are calculated
Amps = watts ÷ volts. For 5,500 W at 240 V that is 22.9 A. The 4,500–5,500 W range covers typical models; the nameplate on an electric water heater gives the exact figure.