How we work these numbers out
One sum, applied the same way to everything, with the inputs stated. If you disagree with an assumption you can see exactly which one it is and change it in the calculator.
The prices we use
These live in one file. Changing a rate here recalculates every page on the site at once, which is the only way a site like this stays honest for longer than a month.
| Tariff | Rate | Checked |
|---|---|---|
| ElectricityOfgem price cap, direct debit, average of England, Scotland and Wales, including 5% VAT. | 26.11p per kWh | 22 August 2026 |
| Mains gasOfgem price cap, direct debit, average of England, Scotland and Wales, including 5% VAT. | 7.33p per kWh | 22 August 2026 |
| Off-peak EV electricityA dedicated overnight EV rate. Not capped, varies by supplier, and normally requires a smart meter. | 7p per kWh | 22 August 2026 |
| Petrol, E10 unleadedUK average pump price, ultra low sulphur unleaded. | 168.14p per litre | 16 September 2026 |
| Diesel, B7UK average pump price, ultra low sulphur diesel. | 190.72p per litre | 16 September 2026 |
| Public rapid chargingWeighted average pay-as-you-go price on 50kW and above chargers. | 80p per kWh | 22 August 2026 |
| Public slow and fast chargingWeighted average pay-as-you-go price on 3kW to 49kW chargers. | 54p per kWh | 22 August 2026 |
| Wood, seasoned logs in bulkSeasoned hardwood logs bought loose by the cubic metre and delivered in bulk, the cheapest common way to buy stove wood. | 6.64p per kWh | 31 August 2026 |
| Wood, kiln-dried netsKiln-dried hardwood logs sold by the net from supermarkets, garages and DIY stores, the usual way to buy without storage for a bulk load. | 15.12p per kWh | 31 August 2026 |
| Water and sewerageCombined volumetric water and wastewater charge, metered. Mean of three large suppliers for 2026/27: Thames Water £4.02, United Utilities £4.75, Anglian Water £5.03 per cubic metre. | £4.60 per cubic metre | 22 August 2026 |
What counts as a use
A use is the thing you actually do: a boil, a wash, a load, a cup, a mile, a page, a night. Where an appliance costs the same whether or not anybody uses it, a fridge or a hot tub, the unit is a day instead, because that is the only honest way to divide it.
Rated power is not measured consumption
A 2kW appliance does not use 2kWh in an hour unless it runs flat out for the whole hour, and most do not. Thermostats cycle the element on and off. Every row in our data says which kind of figure it is and what duty cycle we assumed. Where we have used a rated power and an estimated run time, we say so rather than presenting it as a measurement.
What we leave out
Standby draw, which is now small enough on most modern appliances to be lost in the rounding. The cost of the space a thing occupies. Your time. Interest on the money if you had not spent it. Each of these is real and each would make the sum less checkable, so they are excluded deliberately rather than forgotten.
Standing charges
Electricity and gas standing charges are quoted at the top of every page but are not added into any cost per use. You pay them whether or not you switch anything on, so loading them onto a boil or a wash would tell you something misleading about that boil or that wash.
How often this is rechecked
Every figure carries the date it was last verified, and each one has its own limit rather than sharing a single number, because they move at very different speeds. Pump prices are republished weekly and are refreshed here automatically from the Department for Energy Security and Net Zero release, so the petrol and diesel figures are normally a few days old. Water charges are set once a year.
Where we know in advance that a figure stops being true, it carries an expiry rather than an age limit. The energy price cap is the one that matters: the rates above run to 30 September 2026, and a new cap takes effect on 1 October. The build refuses to publish past that date, so those numbers stop the site rather than quietly going wrong on it. That is the whole point of the guard, and it is why you may occasionally find a figure here that is a few days behind rather than one that is silently a quarter out of date.
Who is doing the working
Cost Per Use is an independent UK site with no retailer, supplier or manufacturer behind it, which is set out on the about page along with how it pays for itself.
Where we could be wrong
Purchase prices are typical retail bands, not a specific model, so the capital part of any figure is the softest part of it. Lifetimes are assumptions. Real usage varies more than any of our other inputs. Where a conclusion depends on one of these rather than on the energy price, we say so on the page rather than in a footnote.
Prices used on this page
- Electricity, 26.11p per kWh. Ofgem price cap, direct debit, average of England, Scotland and Wales, including 5% VAT.. Ofgem energy price cap unit rates and standing charges. Checked 22 August 2026.
- Mains gas, 7.33p per kWh. Ofgem price cap, direct debit, average of England, Scotland and Wales, including 5% VAT.. Ofgem energy price cap unit rates and standing charges. Checked 22 August 2026.
- Petrol, E10 unleaded, 168.14p per litre. UK average pump price, ultra low sulphur unleaded.. Weekly road fuel prices, Department for Energy Security and Net Zero. Checked 16 September 2026.
- Diesel, B7, 190.72p per litre. UK average pump price, ultra low sulphur diesel.. Weekly road fuel prices, Department for Energy Security and Net Zero. Checked 16 September 2026.
- Public rapid charging, 80p per kWh. Weighted average pay-as-you-go price on 50kW and above chargers.. Zapmap EV charging price index. Checked 22 August 2026.
- Water and sewerage, £4.60 per cubic metre. Combined volumetric water and wastewater charge, metered. Mean of three large suppliers for 2026/27: Thames Water £4.02, United Utilities £4.75, Anglian Water £5.03 per cubic metre.. Published 2026/27 household charges, Thames Water, United Utilities and Anglian Water. Checked 22 August 2026.