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 a electric water heater use?
Start with a transparent example, then replace the assumptions with your own wattage, operating time and electricity price.
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.
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