UK Energy Bill Calculator 2026

Gas and electricity bills are one of the biggest variable costs in a UK household budget, and they depend on far more than just how many units you use. Your property type, heating system, household size and current unit rates all interact to produce your final bill. This calculator estimates your annual and monthly energy cost for 2026, broken down by fuel, so you can see roughly where you stand.

How to use the energy bill calculator

Enter your household size, property type and primary heating system first, since the calculator uses these to suggest typical annual electricity and gas figures for a home like yours. You can accept these typical figures, or click “Use typical” at any time to reset them, or overwrite them with your own numbers from a recent bill for a more accurate result. Adjust the unit rates if your own tariff differs from the illustrative defaults shown, which are based on the general level of the Ofgem price cap at time of writing.

How the calculation works

For electricity, the calculator multiplies your annual kWh use by your unit rate, then adds your standing charge multiplied by 365 days, since the standing charge applies every day regardless of how much energy you use. Gas and oil heating work the same way, with gas priced per kWh and oil converted from litres using the standard conversion of around 10.35 kWh per litre of kerosene.

Behind the typical usage figures, the calculator separates your baseline, non-heating electricity use (appliances, lighting, cooking) from your heating demand, then applies a rough efficiency factor depending on your heating system: around 85% for a gas boiler, 80% for an oil boiler, 100% for direct electric heating, since almost all the electricity becomes heat, and a typical coefficient of performance of around 3 for a heat pump, meaning it produces roughly three times as much heat as the electricity it consumes. This is why switching heating systems can change your bill dramatically even at identical unit rates.

Worked example

Take a 3-person household in a semi-detached house with a gas boiler, using this calculator's typical defaults of around 2,700 kWh of electricity and 13,500 kWh of gas a year, at illustrative default rates of 25.7p per kWh for electricity and 6.3p per kWh for gas, plus standing charges.

The electricity portion comes to roughly £880 a year (2,700 kWh at 25.7p, plus the standing charge), and the gas portion comes to around £960 a year (13,500 kWh at 6.3p, plus its own standing charge). Combined, that's an estimated £1,840 a year, or around £153 a month. Now try switching the heating type to a heat pump in the calculator above with the same household details, and you will see the estimated bill change noticeably, since the heating demand is now met by more expensive electricity, but at a much higher efficiency than direct electric heating.

What actually drives your energy bill

Property size and insulation quality matter enormously: a detached house typically has considerably more heating demand than a flat of similar occupancy, simply because there is more external wall and roof area losing heat. Household size affects both heating (more occupants, more hot water and often warmer overall temperatures) and appliance use (more laundry, cooking and device charging). Your heating system's efficiency then determines how much fuel is needed to meet that underlying demand, which is why our loft insulation calculator is worth checking alongside this one if your home is under-insulated.

Common mistakes people make estimating their energy bill

A frequent mistake is comparing a headline unit rate without checking the standing charge, which can vary noticeably between suppliers and applies every single day regardless of usage. Another is assuming national average figures apply directly to an unusually large or small household, when actual usage can differ substantially from the Ofgem reference values used as defaults here. It is also easy to forget that switching to an electric vehicle, adding a home office, or working from home more often can shift electricity use up considerably compared with previous years, making old bills a poor guide to current usage.

Finally, some people assume a heat pump will always be cheaper than gas, when in reality the outcome depends heavily on the relative price of electricity versus gas per kWh at the time, and on the heat pump being sized and installed correctly for the property. Running your own numbers through this calculator, rather than relying on a generic rule of thumb, gives a clearer picture for your specific situation.

Related calculators

If your home is under-insulated, our loft insulation calculator estimates the rolls needed and potential saving from topping up to the recommended depth. If you are budgeting for a house move alongside ongoing running costs like energy, see our mortgage calculator and water bill calculator. To plan towards a specific savings goal, whether for home improvements or a rainy day fund, try our savings goal calculator, and read our guide on how to reduce your energy bills in 2026 for more detailed, room-by-room tips.