Estimate how much electricity an appliance uses and what it costs to run at current UK rates
Knowing how much electricity an appliance uses is the first step to controlling your energy bills. Every electrical device has a power rating measured in watts (W), and the amount of energy it consumes depends on that wattage and how long you use it. Energy consumption is measured in kilowatt-hours (kWh), which is the unit your supplier charges you for. In the UK, the Ofgem energy price cap sets the maximum unit rate for customers on standard variable tariffs. The current cap rate of 24.5p per kWh is used as the default in this calculator, though your actual rate may differ if you are on a fixed deal. By entering the wattage of your appliance, how many hours you use it each day, and the number of days, you can see exactly how much energy it consumes and what it costs. This calculator is particularly useful for identifying energy-hungry appliances. Devices like electric heaters, tumble dryers, and immersion heaters can cost significantly more to run than you might expect. Conversely, modern LED lighting and efficient appliances use very little power. Understanding these differences helps you make informed decisions about which appliances to use, when to use them, and whether upgrading to more efficient models would save you money.
To calculate the electricity consumption and cost of an appliance: 1. Enter the wattage of your appliance. This is usually printed on a label on the device itself, in the user manual, or on the manufacturer's website. Common examples include kettles at 2,000-3,000W, washing machines at 500-2,000W, and LED light bulbs at 5-15W. 2. Enter how many hours per day you typically use the appliance. For devices that cycle on and off (like fridges or central heating), estimate the average active hours. A fridge might run its compressor for about 8 hours out of every 24. 3. Enter the number of days you want to calculate for. The default is 30 days (approximately one month). Use 365 for a full-year estimate, or 7 for a weekly view. 4. The electricity rate defaults to the current Ofgem price cap of 24.5p per kWh. If you know your exact rate from your energy bill or supplier app, enter that instead for a more accurate cost estimate. 5. Review the results showing total kWh consumed, the cost for your specified period, daily usage, and projected annual figures.
The electricity consumption formula converts wattage and usage time into kilowatt-hours: Energy (kWh) = (Wattage x Hours per day x Number of days) / 1,000 The division by 1,000 converts from watt-hours to kilowatt-hours. One kilowatt-hour is the energy used by a 1,000W appliance running for one hour. Cost is then calculated by multiplying the energy consumed by the unit rate: Cost (pence) = kWh x Rate (p/kWh) For example, a 1,000W electric heater used for 4 hours per day over 30 days: Energy = (1,000 x 4 x 30) / 1,000 = 120 kWh. At 24.5p/kWh, that costs 120 x 24.5 = 2,940p, or GBP 29.40. Daily consumption is simply (wattage x hours) / 1,000, and the annual projection multiplies the daily figure by 365 days.
Inputs: Wattage: 2,000W. Hours per day: 4. Days: 30. Rate: 24.5p/kWh.
Inputs: Wattage: 10W. Hours per day: 12. Days: 30. Rate: 24.5p/kWh.
Inputs: Wattage: 2,500W. Hours per day: 1.5. Days: 8 (roughly 2 uses per week for a month). Rate: 24.5p/kWh.