About this calculator
Where does the electricity go? List your appliances with their power, how long they run and how many you have, and the calculator gives the kWh per day, month and year for each and for all of them together. For the cost, multiply the kWh by your own tariff — no prices are built in.
Each new row starts from example values for that kind of appliance — replace them with the figures from the appliance's rating plate or data sheet.
Formula
E_week = n × (P × h × d + P_s × (168 − h × d)) / 1000 kWh
E_day = E_week / 7
E_year = E_day × 365
E_month = E_year / 12
P— power while on, W;P_s— standby power, W (drawn the rest of the week,168 − h × dhours).h— hours a day it is on;d— days a week it is used;n— how many.- Fridges and freezers cycle on and off by themselves, so their row takes
the kWh per year from the EU energy label instead:
E_year = n × E_label.
Worked example
The default rows:
fridge label = 150 kWh/yr
lighting 8 × 10 W, 5 h,
7 days a week = 146 kWh/yr
TV 100 W, 4 h, 7 days
+ 0.5 W standby = 150 kWh/yr
washing m. 1000 W, 1 h, 3 days
+ 0.5 W standby = 161 kWh/yr
kettle 2000 W, 0.2 h,
7 days a week = 146 kWh/yr
total 2.06 kWh/day = 752 kWh/yr
(63 kWh/month)
FAQ
Where do I find an appliance's power? On its rating plate or in the manual (W or kW). For an LED lamp it is printed on the bulb. A plug-in energy meter measures real use, standby included.
Why does my washing machine use less than power × time? Its heater runs only part of the cycle. The default 1000 W is an average over a cycle, not the heater's rating. The EU energy label gives the kWh per 100 cycles: divide it by 100, multiply by 1000 and enter the result as the power (W) for a one-hour cycle.
What about standby? Many devices draw a little power when "off" — a TV, a set-top box, a microwave clock. Small per device, but it runs all year.
Does it include electric heating or a heat pump? Add an electric heater row with its hours, or use the fuel consumption calculator, which works from the building's heat demand.
Assumptions and limits
- Power is constant while on; appliances with a thermostat or a changing load (heaters, ovens, washing machines) use less than their rating × time.
- A year is 365 days; a month is a twelfth of a year.
- Example values in each new row are illustrations only.
- No prices and no costs; multiply the kWh by your own tariff.