From watts to annual cost
Calculate the daily and annual electricity use and running cost of an appliance, machine or group of devices.
Method
Daily energy = watts ÷ 1,000 × hours per day × quantity. Annual cost = daily energy × days used × electricity tariff.
A 1,000 W heater used for 2 hours on 365 days consumes 730 kWh. At €0.30/kWh, that costs €219 per year.
Use responsibly
Nameplate power is often a maximum. Thermostats, standby modes and variable loads mean measured consumption can differ.
Last reviewed: 28 July 2026
Calculation and copy checked for this release.
Practical guide
Learn which capacity, cycling, efficiency, tariff and degradation assumptions drive a home-battery payback estimate and how to test them.
