An energy bill looks like a wall of numbers, but the structure underneath is simple once you know the parts. There are really only two charges, one unit of measurement, and a handful of things worth checking. Read it properly and you can see exactly where your money goes, whether the figures are based on a real meter reading or a guess, and which appliances are quietly draining the most. This guide walks through a typical UK dual-fuel bill at the current Ofgem cap rates so you can do the same with your own.
The short answer. Every UK energy bill has two charges per fuel: a unit rate (the price per kWh of energy you actually use) and a standing charge (a fixed daily fee just for being connected). Electricity is currently capped at 26.11p per kWh plus 57.19p a day, gas at 7.33p per kWh plus 29.04p a day. Multiply your kWh by the unit rate, add the standing charge across the billing days, add VAT, and that is your bill. If it says estimated, the supplier guessed your usage, so send a meter reading.
The kilowatt-hour is the only unit that matters
Everything on the bill is measured in kilowatt-hours, written kWh. A kilowatt-hour is simply a thousand watts running for one hour. A one-bar electric fire (1kW) left on for an hour uses one kWh. A 100-watt item left on for ten hours also uses one kWh. Your meter counts these units as they pass, and that count is what you pay for.
Once you think in kWh, the running cost of anything is just three numbers multiplied together: its power in kilowatts, the hours it runs, and the price per kWh. A 2kW heater for one hour is 2 kWh, which at 26.11p costs about 52p. A 9kW electric shower running for ten minutes is 1.5 kWh, about 39p. That single sum is all our appliance running cost calculator does, and it is the foundation for everything else.
Gas is billed the same way, in kWh, even though your gas meter often shows cubic metres or hundreds of cubic feet. The supplier applies a conversion factor (printed on the bill) to turn the volume into kWh before charging you. You do not need to do that maths yourself, but it explains why the gas meter reading and the kWh on the bill are different numbers.
Two charges per fuel: unit rate and standing charge
This is the part that confuses people most. For each fuel you pay two separate things.
- The unit rate is the price for each kWh you actually burn. Use more, pay more. This is the bit you can cut by using less.
- The standing charge is a fixed daily fee you pay no matter what, even if you use nothing at all. It covers the cost of keeping you connected to the network, meter maintenance, and various policy costs bundled in over the years.
Here are the current capped rates for a typical direct-debit dual-fuel home.
| Charge | Electricity | Gas |
|---|---|---|
| Unit rate (per kWh) | 26.11p | 7.33p |
| Standing charge (per day) | 57.19p | 29.04p |
| Standing charge (per year) | £208.75 | £106.00 |
At 26.11p/kWh electricity and 7.33p/kWh gas, Ofgem cap July to September 2026. Worked examples; check your own tariff.
The standing charge matters more than people expect. Between the two fuels you are paying about 86p a day, or roughly £315 a year, before you use a single unit. For a light user, that fixed cost can be the largest part of the bill, which is why cutting usage has a floor. It is also why standing charges are worth understanding on their own, and why the cheapest tariff for a heavy user is rarely the cheapest for a light one.
A worked example bill
Take a typical household over a 30-day month using 250 kWh of electricity and 800 kWh of gas (gas is higher in winter, lower in summer). Here is how the bill builds up.
| Line | Working | Cost |
|---|---|---|
| Electricity used | 250 kWh at 26.11p | £65.28 |
| Electricity standing charge | 30 days at 57.19p | £17.16 |
| Gas used | 800 kWh at 7.33p | £58.64 |
| Gas standing charge | 30 days at 29.04p | £8.71 |
| Subtotal before VAT | £149.79 | |
| VAT at 5% | £7.49 | |
| Total for the month | £157.28 |
At Ofgem cap rates July to September 2026. Domestic energy carries 5% VAT, not the usual 20%. Your own usage and billing period will differ.
Lay your real bill next to this and every line should map across: a usage figure in kWh times a unit rate, plus a daily charge times the number of days, plus 5% VAT. If a number does not add up, that is your cue to query it.
Estimated versus actual readings
Look for the letter beside each meter reading. An A means actual, a reading taken from the meter (by you, the supplier, or a smart meter). An E means estimated, which means the supplier has guessed your usage based on past patterns. Estimates can be well out in either direction.
A pessimistic estimate bills you for more than you used and builds up credit the supplier sits on. A cheery one underbills you and quietly builds a debt that lands later as a catch-up demand. Neither is what you want.
The fix is simple: submit your own meter reading, ideally monthly, or on the day a bill is generated. If you have a smart meter working properly, it sends actual readings automatically and the E should disappear. If your smart meter has gone dumb (a common problem after switching supplier), go back to reading it yourself until it is fixed.
Working out where the money actually goes
The bill tells you the total, but not which appliances drove it. Two approaches close that gap.
The direct method: note your electricity meter reading, run one appliance for a known time with as little else on as possible, then read the meter again. The difference is the kWh that appliance used, and multiplying by 26.11p gives its cost. A plug-in energy monitor does the same job far more conveniently, showing live watts and totting up kWh over days.
The shortcut: the usual suspects are predictable. Anything that makes heat is expensive, because heat needs a lot of power. The tumble dryer, the electric shower, the kettle, the oven and any electric heating dominate the electricity side. On gas, it is almost entirely your central heating and hot water. The always-on items, the fridge-freezer and the router, are individually small but add up because they never switch off. The wider electricity picture is set out on the electricity hub.
Credit, debit and how direct debit is set
If you pay by monthly direct debit, your payment is not your usage. The supplier estimates your whole year's energy, totals the cost, and divides by twelve so you pay a flat amount each month. You build up credit in summer when you use less, and draw it down in winter when you use more. Over a full year it should roughly balance.
Two things go wrong. If the estimate is too high, you pile up a large credit balance, effectively an interest-free loan to the supplier, and you can ask for it back if it grows beyond a sensible buffer. If the estimate is too low, you slide into debt that lands as a payment increase later. Both come from the supplier guessing your usage, which is why sending regular meter readings matters: accurate readings keep the direct debit set at a fair level. Check your balance a couple of times a year, especially at the end of winter and the end of summer.
What the cap does and does not do
The headline figure of £1,663 a year that you see in the news is the Ofgem price cap for a household using a typical amount of energy. It is widely misunderstood. The cap does not limit your total bill; it caps the unit rate and the standing charge. If you use more than typical, you pay more than £1,663. If you use less, you pay less. There is no ceiling on the total, only on the price per unit.
The cap is also not the cheapest deal available. It is a backstop for anyone on a standard variable tariff. A genuine market comparison can sometimes beat it, which is covered in switching suppliers and in detail in how the energy price cap works. The cap changes every three months, so the figures here are for July to September 2026 and will move.