How the SwitchPilot calculator works
Every energy bill in Great Britain is built from the same two sums, one for electricity and one for gas:
unit rate × kWh used + standing charge × days in the period
The unit rate is what a supplier charges for each kilowatt hour of energy, quoted in pence. The standing charge is a fixed daily fee that applies whether or not any energy is used. Add the two together, divide by 100, and the result is the bill in pounds. Electricity and gas are worked out separately and then added, because each fuel has its own unit rate and its own standing charge.
Rates are regional. Great Britain is divided into fourteen electricity distribution regions, and the network costs baked into every tariff differ from one to the next. That is why this page asks for a postcode first: SwitchPilot reads the region from the opening letters, then prices the home on that region's rates instead of a national average. Two identical homes in different regions will land on different numbers for exactly the same usage.
All prices on this page assume payment by monthly Direct Debit and include VAT at the rate applying in the cap period shown, which is the same basis Ofgem uses when it publishes the default tariff cap. Prepayment and standard credit customers pay on a different basis, so the figures here will not match those methods exactly.
The comparison tariffs in the picker are refreshed from the SwitchPilot tariff feed, all_tariffs.json, which is rebuilt from supplier data rather than typed in by hand. The status strip under the tool shows whether that feed loaded live. The default tariff behind the headline estimate is the regional Ofgem cap, which is the rate a household falls back on when it has not chosen a fixed deal.
Usage is the part that varies most between homes. The presets behind the 1-2 bed, 2-3 bed and 4+ bed options are starting points, not measurements of any particular house. For the national reference figures Ofgem itself uses, see the SwitchPilot analysis of Ofgem's typical domestic consumption values. Anyone who knows their own annual kWh from a bill can tune the appliances above until the totals match.
What each appliance costs to run
The table below prices a 2-3 bed home in London on the Ofgem default tariff, using the same appliance model as the tool above. It updates when the postcode, home size or appliance settings change, so it always reflects the home currently on screen.
Estimated running costs, 2-3 bed home in London, Ofgem default tariff, including VAT
| Appliance | Typical use | Energy a year | Cost a year | Fuel |
|---|
| Fridge / freezer | 24 hours a day | 350 | £93 | Electricity |
| Kettle | 3 boils a day | 131 | £35 | Electricity |
| Microwave | 2 uses a day | 73 | £19 | Electricity |
| Hob | 0.4 hours a day | 292 | £24 | Gas |
| Washing machine | 3 loads a week | 125 | £33 | Electricity |
| Tumble dryer | 3 loads a week | 313 | £83 | Electricity |
| Dishwasher | 3 loads a week | 156 | £41 | Electricity |
| Oven | 0.4 hours a day | 263 | £21 | Gas |
| TV & media | 3 hours a day | 88 | £23 | Electricity |
| Lighting | 5 hours a day | 110 | £29 | Electricity |
| Sockets & misc | 2.8 kWh a day | 1,022 | £272 | Electricity |
| Central heating | 6 hrs a day in winter, 0 in summer | 7,416 | £604 | Gas |
| Shower (hot water) | 21 minutes a day | 1,278 | £104 | Gas |
| Computers | 5 hours a day | 137 | £36 | Electricity |
Figures are annual estimates from the usage settings shown in the tool above, priced at the regional default tariff. Heating dominates most homes, which is why the thermostat control has more effect on the total than any single appliance. A cheaper tariff could save money against the default tariff, but it does not change the kWh in this table.
Frequently asked questions
How do you calculate your electricity bill?
Multiply the electricity you use over the period, measured in kWh, by your unit rate in pence per kWh. Then add your standing charge multiplied by the number of days. Divide the total by 100 to turn pence into pounds. The SwitchPilot calculator does both halves once you enter a postcode and pick a home size, and it applies the rate for your region rather than a national average.
How do you calculate your gas bill?
Gas works the same way as electricity: annual kWh multiplied by the gas unit rate, plus the gas standing charge for every day in the period. The wrinkle is that a gas meter records cubic metres or hundreds of cubic feet, not kWh, so a supplier applies a volume correction and a calorific value before billing. This calculator models gas in kWh throughout, which is the unit printed on the bill.
What is a standing charge?
A standing charge is a fixed daily fee for being connected to the network. It covers meters, cables, pipes and the cost of suppliers that have failed, and it is billed whether or not any energy is used. Electricity and gas each carry their own standing charge. Because network costs differ around Great Britain, standing charges vary noticeably from one region to the next.
How does your postcode affect your energy bill?
Great Britain is split into fourteen electricity distribution regions, and each one carries its own network costs. Those costs feed into both the unit rate and the standing charge, so two identical homes in different regions pay different amounts for exactly the same usage. SwitchPilot reads the region from the opening letters of a postcode and prices the home on the matching regional rates.
How much energy does a typical UK home use?
Ofgem publishes typical domestic consumption values, and those are the usage figures behind every headline price cap number. The SwitchPilot review of Ofgem's typical usage figures covers the latest set and what changed. They are averages across the country, so this calculator starts from the home size selected above and then lets every appliance be tuned from there.
How can you check what you are actually paying?
The unit rate and standing charge are printed on the bill or shown in an online account, usually alongside the tariff name. Anyone who would rather not hunt for them can use the SwitchPilot AI bill scanner, which reads a photo of a bill and pulls out the rates, the usage and the tariff. Those rates can then be typed into the tariff panel above under "My own rates".
See EDF FreePhase Dynamic →
See So Energy tariffs →