Electricity Consumption and Bill Calculator

How is electricity use calculated?

The energy an appliance uses is its power multiplied by the time it runs. Bills are in kilowatt hours (kWh): a 1000 watt appliance running for one hour uses 1 kWh.

kWh = power (W) × quantity × hours / 1000

For the monthly figure, multiply the daily value by the number of days the appliance is used each month. The tool does this for every appliance, adds them up and shows the share each one takes of the bill.

Example

A fridge that draws 150 W, with the compressor running 8 hours a day in total, uses 150 × 8 / 1000 = 1.2 kWh a day and 36 kWh a month. A 2000 W washing machine run for an hour 12 times a month comes to 24 kWh. Eight 10 W LED bulbs on for 5 hours a day use 12 kWh a month.

The bill

The total kWh is multiplied by the unit price. A fixed monthly charge is added if there is one, and the tax percentage is applied to the sum. Take the unit price and tax rate from your own bill: tariffs depend on the country, the customer group and the period, and the tool assumes no value. There is no need to enter a currency. The result is in the currency of the price you enter.

Where do I find the power?

It is printed in watts (W) on the rating plate or in the manual. That figure is usually the maximum. Appliances with a thermostat, such as fridges, air conditioners, irons and ovens, do not run at full power all the time, so for these enter the hours the compressor or heater is actually on. A plug in energy meter gives the most accurate figure.

Limits

The calculation uses a single unit price. With tiered tariffs (higher price above a threshold) or time of use tariffs (day, peak, night) you can approximate the result with an average price. Standby consumption is not included unless you add it as a line of its own. The appliances and wattages shown at first are only a sample.