Electric water heater: how much battery you need
Electric water heater (tank) draws about 3750 W (3000–4500 W range), runs 40% of the time and uses 4500 Wh per day. Start-up surge: 4500 W.
A US tank heater runs on 240 V at up to 4,500 W; heat water on the generator, or skip it on battery. Champion lists 3000–4500 W running; we use the middle for energy and the top starting figure (4500 W) for the peak.
Battery needed
| Hours | Wh | Battery (Wh) | Inverter (W) |
|---|---|---|---|
| For 8 hours | 1500 | 2273 | 4125 / 4500 |
| For 24 hours | 4500 | 6819 | 4125 / 4500 |
| For 72 hours | 13500 | 20455 | 4125 / 4500 |
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Stations that fit (24 h)
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FAQ
How many watts does a Electric water heater (tank) use?
Typically 3750 W while running, with a range of 3000–4500 W depending on model and age. Start-up surge can reach 4500 W.
How long will a 1000 Wh power station run a Electric water heater (tank)?
About 0.4 hours on the clock, allowing for the 40% duty cycle, inverter losses and a 20% reserve.
What size power station do I need for a Electric water heater (tank) overnight (8 h)?
About 2273 Wh of battery and an inverter rated at least 4125 W continuous with 4500 W surge.
Can I run a Electric water heater (tank) on solar during an outage?
You need roughly 3000 W of panels in winter to replace a day's use (4500 Wh), charging through a station with a big enough MPPT input.
Other appliances
1 Approximate values: estimated from motor or heater power and typical figures published online, not from a manufacturer chart. Check your appliance label.
Inverter efficiency 88%, usable depth of discharge 90%, reserve 20%. Full method: How we calculate. source