Electricity Cost Calculator
Work out how much electricity an appliance uses and what it costs to run per year, per month and per day, including standby power.
Cost per year
£37.96
Cost per month
£3.16
Cost per day
£0.10
Use per year
146 kWh
Of which standby, per year
£0.00
Please note: The result is an estimate and has been rounded. Actual costs and values may differ, and no rights can be derived from this calculation.
Standing charges, fixed fees and prices that change by the hour or season are not included.
How this number is calculated
The blocks use your input. Change a value above and they update with it.
Step 1 · Hours on per week
Step 2 · Use while on, per year
Step 3 · Standby use per year
Step 4 · Use per year
Step 5 · Cost per year
How the calculation works
Work out what an appliance costs to run per year, per month and per day. Enter its power, how long it is on and your electricity price. Standby power can be included.
Energy use in kilowatt hours (kWh) is the power in kilowatts times the number of hours. A 100-watt appliance that is on for 10 hours uses 1 kWh. The calculator counts the hours per week that the appliance is on, and counts the remaining hours of the week as standby. It converts that to a year of 365 days, and multiplied by your price per kWh that gives the cost per year. Per month is one twelfth of that, per day one 365th.
Formula
Hours on per week = hours per day × days per week. Use per year (kWh) = (power × hours on + standby power × (168 − hours on)) ÷ 1000 × 365 ÷ 7. Cost per year = use per year × price per kWh.
Assumptions
- The power is the average use while the appliance is on. The rating plate often shows the maximum; a fridge or washing machine uses less on average.
- Standby power applies to all hours the appliance is not on.
- The electricity price is a fixed amount per kWh, including taxes. Standing charges and fixed fees are not included: you pay those with or without the appliance.
- A year has 365 days; a month is one twelfth of a year.
Example calculations
The button fills in the calculator above, so you can carry on from there.
-
TV with standby power
Cost per year
£61.00
Power (watts) 120 · Hours on per day 5 · Days per week 7 · Standby power (watts) 1 · Electricity price per kWh £0.27
-
Tumble dryer, 3 times a week
Cost per year
£105.59
Power (watts) 2,500 · Hours on per day 1 · Days per week 3 · Standby power (watts) 0 · Electricity price per kWh £0.27
-
Router that is always on
Cost per year
£23.65
Power (watts) 10 · Hours on per day 24 · Days per week 7 · Standby power (watts) 0 · Electricity price per kWh £0.27
Frequently asked questions
Where do I find the power of an appliance?
On the rating plate or in the manual, in watts (W). That is often the maximum. To measure the actual use, put a plug-in energy monitor between the socket and the plug: it shows the power and the kWh.
What is standby power?
Electricity an appliance uses while it is off or on standby, for example for a light, a clock or the remote control. It seems small, but it runs all year: 5 watts of standby power is 43.8 kWh a year, 11.39 at a price of 0.26 per kWh.
Which electricity price should I enter?
The price per kWh from your contract or bill, including taxes. With a time-of-use or dynamic tariff, use an average. If you have solar panels, electricity you use straight from them costs less.
How do I convert watts to kWh?
Multiply the power in watts by the number of hours and divide by 1,000. A 2,000-watt kettle that is on for 3 minutes (0.05 hours) uses 2,000 × 0.05 ÷ 1,000 = 0.1 kWh.
What does an appliance that is always on cost?
An appliance that runs day and night is on for 8,760 hours a year. A 10-watt router then uses 87.6 kWh a year, 22.78 at a price of 0.26 per kWh.
Sources and checks
Sources
How we check it
This calculator has 13 fixed checks: 8 calculations with a result that is fixed in advance, and 5 cases of invalid input that must be rejected. They all run automatically every time we publish; if one fails, the calculator does not go live.
See the calculations
- Power (watts) 100 · Hours on per day 4 · Days per week 7 · Standby power (watts) 0 · Electricity price per kWh £0.27 → Cost per year £39.42
- Power (watts) 120 · Hours on per day 5 · Days per week 7 · Standby power (watts) 1 · Electricity price per kWh £0.27 → Cost per year £61.00
- Power (watts) 2,500 · Hours on per day 1 · Days per week 3 · Standby power (watts) 0 · Electricity price per kWh £0.27 → Cost per year £105.59
- Power (watts) 400 · Hours on per day 3 · Days per week 5 · Standby power (watts) 5 · Electricity price per kWh £0.27 → Cost per year £95.24
- Power (watts) 10 · Hours on per day 24 · Days per week 7 · Standby power (watts) 0 · Electricity price per kWh £0.27 → Cost per year £23.65
- Power (watts) 0 · Hours on per day 0 · Days per week 7 · Standby power (watts) 5 · Electricity price per kWh £0.27 → Cost per year £11.83
- Power (watts) 1,000 · Hours on per day 2 · Days per week 7 · Standby power (watts) 0 · Electricity price per kWh £0.25 → Cost per year £182.50
- Power (watts) 100 · Hours on per day 4 · Days per week 7 · Standby power (watts) 0 · Electricity price per kWh £0.00 → Cost per year £0.00
Changes
- : First version. Default electricity price 0.26 per kWh, as under the Ofgem price cap from October 2026. Sources added.
Last reviewed: · How we build and check our calculators
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