How many watts does an electric water heater use
While it runs, an electric water heater draws 3,000 to 4,500 W, and it has no starting surge. The smallest portable that can run it has 6,500 W.
Watts for running and for starting
| Load | Running | Starting |
|---|---|---|
| Electric water heater | 3,000 to 4,500 W | no surge |
This comes from the Champion wattage chart, 04-17-26. On your own electric water heater, the nameplate lists the exact figure in watts or amps. Multiply amps by 120 V. Use 240 V only for a two-pole breaker load, such as a well pump.
The smallest generator for starting it
A generator must handle 4,500 W, with that load staying within 80% of its rating. To meet both needs, the smallest common portable is 6,500 W. Other loads add their running watts to that generator as well.
Other loads with an electric water heater
| Electric water heater plus | Running | Peak at a start | Smallest portable |
|---|---|---|---|
| lights, TV and the router | 5,070 W | 5,070 W | 6,500 W |
| a freezer and lights | 5,150 W | 5,650 W | 6,500 W |
| a 1/2 hp sump pump and lights | 5,700 W | 6,800 W | 7,500 W |
| a microwave | 5,700 W | 5,700 W | 7,500 W |
| a 1 hp well pump | 6,500 W | 8,500 W | 10,000 W |
| a window AC, 10,000 BTU | 5,700 W | 6,900 W | 7,500 W |
Running watts add up, and only the largest motor start sits on top of the total. A portable's starting output is about 25% higher than its running rating. The appliance wattage chart lists every load.