Standby cost calculator
Estimate standby electricity costs and compare a lower-power scenario using your own measured figures.
The 5W starting figure is hypothetical. Enter measured idle input for a device or group; it is not a UK household average or a guaranteed saving.
Reference: Ofgem GB average Direct Debit rate, 1 October–31 December 2026: 26.32p/kWh. Checked 8 November 2026. Use your own bill; regional and payment-method rates differ, and Northern Ireland has a separate market. Annual costs hold the entered rate constant; they are not a forecast. Standing charges are excluded. For time-of-use tariffs, calculate each rate's consumption separately and add the costs.
Both scenarios use the same idle schedule. Include any replacement control's own consumption in the alternative figure.
Estimated annual electricity cost
43.80 kWh per year · £0.96 per average month · £0.03 per average day
Potential annual reduction: £11.53.
Switch off only equipment that can safely be disconnected under its instructions. Keep essential equipment and appliances intended for continuous use powered as required. This tool does not identify which devices are safe to switch off. Measure standby energy.
Worked example: A smaller measured idle load
These fixed teaching inputs are separate from the editable calculator above and are not current tariff or product claims.
- Inputs
- Current idle input 5W; alternative 1W; both for 24 hours a day over 365 days.
- The working
- Current: 43.8kWh/year. Alternative: 8.76kWh/year. Difference: 35.04kWh.
- The result
- £10.95 versus £2.19 per year; potential reduction £8.76. The alternative is only relevant where it is safe and practical for the equipment.
How this calculator works
Annual idle kWh = watts ? 1,000 ? idle hours per day ? days used. Apply the same schedule to current and alternative input. Potential reduction is their cost difference, which can be zero or negative.
Cost in pounds = energy in kWh × electricity rate in pence ÷ 100. Monthly costs are annual costs divided by 12; daily costs are divided by 365. These are averages over a year. Calculations retain precision until display rounding.
Get a more useful estimate
Read our step-by-step guide to measuring appliance electricity before treating a nameplate rating as a measured average.
Start with the rate on your bill and energy information for your exact model. A plug-in energy monitor can help measure suitable plug-in appliances; follow its safety instructions and power limits. Do not apply full-power wattage for 24 hours to a cycling fridge or freezer.
What is excluded?
The day/night comparison includes the standing charges you enter; appliance-only tools exclude them. Gas, water, detergent, maintenance, discounts and purchase costs are excluded unless the tool explicitly asks for a purchase premium. Usage and tariffs can change. The reference tariff covers Great Britain and does not represent Northern Ireland or every contract.
Read our sources and assumptions →Common questions
How do I find standby watts?
Use a suitable measurement for the actual idle mode, including connected/network functions you normally leave enabled. A short display reading may miss intermittent activity. A longer kWh measurement can be converted to average watts by dividing by elapsed hours and multiplying by 1,000.
Should I switch off every device to get the calculated saving?
No. The calculation only compares your entered energy assumptions. Equipment needed continuously or required to remain on under its instructions must be treated separately. Include the power of any timer, smart plug or replacement control in the alternative scenario.