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Electricity Cost Calculator
What a device costs to run per day, month and year.
Free tools that run in your browser. Nothing you type, open or create is uploaded to NerdBible or anyone else.
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The price per kWh is on your electricity bill or your supplier's tariff page, usually labelled unit rate. It is not filled in for you because it varies by country, supplier, tariff and time of day. A standing or daily charge is not included, since you pay it whether or not the device is on. The currency only changes the symbol shown; nothing is converted.
How to use it
- Enter the device's power in watts, from its label, manual or a plug-in power meter.
- Enter how many hours a day and how many days a week it runs.
- Enter your price per kWh from your bill and pick the currency symbol to show.
- Tick standby if the device draws power when switched off, and enter that figure.
Questions
How is the cost worked out?
Watts times hours gives watt hours; divide by 1,000 for kilowatt hours (kWh), the unit on your bill. Multiply by your price per kWh. A 100 W device running for 10 hours uses 1 kWh.
Where do I find a device's wattage?
On the rating label or the power adapter, or in the manual. If it only shows volts and amps, multiply them. For devices whose draw changes, such as a fridge, a computer or a TV, a plug-in power meter gives the real average.
What is standby power?
Power a device draws while switched off but still plugged in, for a clock, a remote control receiver or a network connection. It is often under 1 W per device, but older devices and anything that stays connected can draw more. Here it counts for every hour the device is not in use.
How is a month counted?
As an average month, a year divided by 12 (about 30.4 days), and a year as 365 days. The per day figure is an average across the week, so it already reflects the days you set.
About this tool
How much does it cost to run an appliance?
Electricity is billed per kilowatt-hour (kWh): the energy used by a 1000 watt device running for one hour. Once you know a device's power and how long it runs, the cost is simple arithmetic, and this calculator does it for you.
The formula
Watts multiplied by hours of use, divided by 1000, gives kWh. Multiply that by your price per kWh for the cost. A 2000 W heater running 3 hours a day uses 6 kWh a day; at 0.30 per kWh that is 1.80 a day, about 55 a month.
What you enter
- The device's power in watts, from its label, manual or charger.
- How many hours a day it runs, and how many days a week.
- How many of the device you run, and its standby draw if it uses power when switched off.
- Your price per kWh, found on your bill or tariff. Any currency works; the symbol is only for display and nothing is converted.
The result shows the energy and cost per day, week, month and year, which makes it easy to compare an old appliance with a new one or to see what standby power adds up to.
Getting a realistic number
Many appliances do not draw their full rated power all the time. Fridges, freezers and heat pumps cycle on and off, and a television varies with brightness. A plug-in power meter gives the true figure for those. Tariffs with different day and night rates need the rate for the hours the device actually runs.
Calculations run in your browser; nothing is sent anywhere.
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