Estimate appliance electricity use and cost from wattage, daily running time, your tariff and standing charge.
The standing charge applies to the whole electricity supply, not to each appliance. Do not add it again when comparing several appliances for the same period.
How to use the Electricity Cost Calculator UK
Enter the appliance wattage, quantity, estimated hours used each day and the number of days. Then copy the electricity unit rate from your latest bill or tariff. The daily standing charge is optional and should only be included when estimating the total supply cost for the period.
Electricity cost formula
Electricity is billed in kilowatt-hours (kWh). The calculator converts watts to kilowatts, multiplies by the number of appliances and running hours, then applies the unit price.
| Step | Formula |
|---|---|
| Daily electricity use | (Watts ÷ 1,000) × quantity × hours per day |
| Period electricity use | Daily kWh × number of days |
| Usage cost | Period kWh × unit rate in pounds |
| Total estimate | Usage cost + standing charge for the period |
Unit rate and standing charge
The unit rate is the amount charged for each kWh of electricity. The standing charge is a fixed daily amount for keeping the property connected, even on a day when no electricity is used. Ofgem explains that price-cap rates can vary by region, payment method and meter type, so the figure on your own tariff is the best input. Check the latest Ofgem energy price cap unit rates and standing charges.
How to improve the estimate
Rated wattage is not always the same as continuous consumption. Thermostatically controlled appliances may switch on and off, while devices with different power modes can change their usage. A plug-in energy monitor or smart-meter reading can provide a better kWh figure for equipment with variable demand.
Plan household and renovation energy costs
For project quantities, use the Building Materials Calculator. You can combine material and power estimates with the Home Renovation Cost Calculator UK. To examine capped tariff costs separately, visit the Energy Price Cap Calculator UK. More practical tools are available on the United Kingdom Calculator homepage.
Frequently asked questions
How do I convert watts into kWh?
Divide watts by 1,000 to get kilowatts, then multiply by the number of hours used.
Should I include the standing charge?
Include it when estimating the whole electricity supply cost. Leave it blank when comparing only the running cost of an appliance.
Where can I find my unit rate?
It is shown on your electricity bill, tariff summary or supplier account, usually in pence per kWh.
Does the energy price cap limit my total bill?
No. It limits relevant tariff rates, not the total amount paid. Higher electricity use still produces a higher bill.
Why might the actual cost differ?
Actual consumption can vary with appliance cycles, settings, efficiency, weather and the exact tariff applied by the supplier.