Electricity consumption and cost calculator
What an appliance costs per month and per year based on hours of use.
Calculator inputs
Results
Enter your values and press “Calculate” to see the result.
In short
- What it calculates
- What an appliance costs per month and per year based on hours of use.
- Formula used
kWh = (watts × hours × days) ÷ 1000- Example
- A 2,000 W heater used 3 hours a day for 30 days at £0.18 per kWh:
Electricity consumption calculator
Knowing what each appliance costs is the first step to cutting the bill. With the wattage and the hours of use, the rest is arithmetic.
The power rating is usually on the appliance label or in its manual.
How it works
Watts are multiplied by hours and divided by a thousand to get kilowatt hours. Multiplying by the price per kWh gives the cost.
Formula
kWh = (watts × hours × days) ÷ 1000
Cost = kWh × price per kWh
Annual cost = watts × hours × 365 ÷ 1000 × price
Worked example
A 2,000 W heater used 3 hours a day for 30 days at £0.18 per kWh:
kWh = (2,000 × 3 × 30) ÷ 1000 = 180 kWh
Cost: £32.40
Annual cost if used all year: £394.20
Explanation
The appliances that cost most are not the ones you think
A phone charger left in the socket uses a negligible amount. What drives the bill is anything that makes heat or cold: oven, hob, tumble dryer, water heater, air conditioning and electric heating. An electric water heater alone can account for a quarter of a home's consumption.
Standby consumption is real, but small
A modern television at rest uses less than a watt, and European rules cap that consumption. Adding up every appliance in a house, standby usually lands between two and seven per cent of the total. It is worth reducing, but it is not where the big saving is.
Contracted power and consumption are different things
The bill has two parts: a fixed charge for the power capacity you have contracted, paid whether you use it or not, and a variable charge for energy consumed. Lowering contracted capacity saves money without changing habits, provided the breaker does not trip when several appliances run at once.
The time of day matters as much as the appliance
With time-of-use tariffs, running the washing machine off-peak can cost half what it does at peak for exactly the same consumption.
Frequently asked questions
Where do I find the appliance wattage?
On the rating plate, usually on the back or underside, given in W or kW.
Does standby mode use power?
Yes. Typically 1 to 5 W per device, little on its own but significant across many devices running 24 hours a day.
Which appliance uses the most?
Those producing heat or cold: water heater, oven, tumble dryer, air conditioning and electric heating. They far exceed consumer electronics.
Is it worth lowering my contracted capacity?
It is usually the most direct saving, because the fixed charge applies whether you consume or not. The limit is not tripping the breaker with several appliances at once.
Need to calculate something else?
These tools are often used alongside this calculator.
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