Watts to kWh
kWh = (W ÷ 1,000) × hours × load factor. Multiply kWh by your electricity price to estimate energy cost.
🚿 Worked example
How much electricity does an electric water heater use?
Compare days with hot-water use against low-use days. Replace example inputs with your own usage pattern.
4.50 kWhper day of use
27.00 €per month at 0.20 €/kWh
Worked example
2000 W × 3 h/day × 75 % load factor × 30 days.
135.00 kWh/month · 324.00 €/year
This is an energy-only estimate. Your bill can also include standing charges, taxes and other household consumption.
Typical reference range
Use the label, manual or manufacturer data for your exact model whenever possible.
| Type or situation | Indicative reference |
|---|---|
| Small 30–50 L tank | 1,200–1,500 W |
| 80–100 L tank | 1,500–2,000 W |
| Large tank | 2,000–3,000 W |
What changes the result?
Rated watts are only one part of the calculation.
Measure when possible
Thermostats, compressors, inverter control and programmes can make real consumption lower or higher than a simple maximum-power estimate.
Practical checks
- Insulation and hot-water demand strongly affect daily energy.
- Avoid unnecessarily high thermostat settings.
- Check for dripping safety valves or hot-water leaks.
Compare more appliances
Return to the appliance library or use the general electricity calculator for any device.
NEXT STEP
Keep exploring
Why water-heater consumption varies so much
Tank water heaters cycle to replace heat lost from the stored water and to reheat water after showers or other hot-water use. That means the same heater can consume very different amounts in two homes even when the rated wattage is identical.
Four variables to check
- Hot-water demand: number and length of showers, taps and other uses.
- Tank size and insulation: larger tanks store more water, but heat loss also matters.
- Thermostat setting: higher stored-water temperature generally increases heat loss.
- Incoming-water temperature: colder inlet water requires more energy to heat.
Estimate over a full day
Short spot measurements can miss reheating cycles. A daily or multi-day observation is more representative, especially when demand changes between weekdays and weekends. Use the electricity consumption calculator to test different operating times.
If you are comparing systems rather than just estimating one heater, see electric water heater vs heat-pump water heater. For Spain, you can apply the current electricity price.
Editorial review: 11 Oct 2026. The worked example is illustrative; real use depends on household demand and installation conditions.
BRICODATO · PRACTICAL CHECK
Check the real energy use of your electric water heater
A storage water heater draws energy both to replace hot water used and to cover tank heat losses. Element wattage alone does not reveal daily kWh. Compare storage capacity, hot-water demand, insulation and the manufacturer's recommended settings rather than simply lowering temperatures without considering hygiene.
Checklist to reproduce the comparison
- Compare days with hot-water use against low-use days.
- Check tank insulation condition and any leakage.
- Do not make unsafe temperature or electrical changes merely to save energy.
The figures elsewhere on this page are illustrative assumptions, not a measured average for every model. Use the label, your actual cycle count and safely collected kWh readings.