How running costs work
Electricity is sold by the kilowatt hour (kWh), often called a unit. One kWh is the energy used by something drawing 1,000 watts (1kW) for one hour. A 3,000-watt kettle uses a unit in 20 minutes. A 100-watt TV takes 10 hours to use the same unit.
Your supplier charges a price for each unit you use, plus a daily standing charge that you pay whatever you use. The standing charge does not change when you switch an appliance on or off, so the running cost of an appliance is only the units it uses multiplied by the unit rate.
Two things decide the bill for an appliance: how powerful it is, and how long it runs. A powerful appliance used briefly, like a kettle or a hair dryer, can cost less over a year than a small one that runs for hours every day, like a dehumidifier.
The sum, step by step
The calculation has three steps. Here it is for a 3,000-watt kettle boiled for 3 minutes, at the price cap rate.
- Power in kilowatts3,000 watts ÷ 1,0003 kW
- Time in hours3 minutes ÷ 600.05 hours
- Units used3 kW × 0.05 hours0.15 kWh
- Cost0.15 kWh × 26.32p3.9p
Some appliances do not run at full power the whole time. An oven, an oil-filled radiator or a fridge has a thermostat that switches the heating element or compressor on and off once it reaches temperature. The calculator has a “share of time drawing power” setting for this under More options.
Which unit rate to use
The calculator starts with the Ofgem price cap rate for electricity from 1 October to 31 December 2026: 26.32p per kWh, the average for Great Britain paying by Direct Debit. From July to September 2026 it was 26.11p.
The government removed VAT from household electricity from 1 October 2026 to 31 March 2027, so the 26.32p rate includes no VAT. Without that change, the rate would be about 5% higher. Gas still carries 5% VAT.
The cap is an average. Rates differ by region and by payment method, and fixed tariffs have their own prices. For the most accurate answer, take the unit rate from your latest bill or your supplier’s app and enter it under More options.
Next price cap
Ofgem is due to announce the cap for January to March 2027 on 25 November 2026. If the unit rate changes, every figure here changes in proportion.
Typical costs of common appliances
These are typical wattages and use, at 26.32p a unit. Your own appliance may use more or less: check its rating plate.
| Appliance | Typical use | Each use | A year |
|---|---|---|---|
| Kettle (3kW) | 3 min, 4 a day | 4p | £57.64 |
| Microwave (1.2kW) | 5 min, 2 a day | 3p | £19.21 |
| Air fryer (1.5kW) | 20 min, 1 a day | 13p | £48.03 |
| Electric oven (2.4kW) | 45 min, 1 a day | 28p | £103.75 |
| Washing machine, 40°C | 4 a week | 20p | £41.17 |
| Tumble dryer (2.5kW) | 75 min, 3 a week | 82p | £128.66 |
| Heat pump tumble dryer | 2 hours, 3 a week | 42p | £65.88 |
| Dishwasher | 5 a week | 26p | £68.62 |
| Fridge freezer | Always on | 19p a day | £69.17 |
| Electric heater (2kW) | 3 hours a day | £1.58 | £576.41 |
| Oil-filled radiator (1.5kW) | 4 hours a day | 95p | £345.84 |
| Dehumidifier (300W) | 8 hours a day | 63p | £230.56 |
| Electric shower (9.5kW) | 8 min a day | 33p | £121.69 |
| Immersion heater (3kW) | 1 hour a day | 79p | £288.20 |
| TV (100W) | 4 hours a day | 11p | £38.43 |
| Games console (150W) | 2 hours a day | 8p | £28.82 |
The biggest users
Anything that heats, or that runs for many hours, tends to top the list. With typical use, these cost the most over a year at the price cap rate:
Ofgem’s typical home uses 2,500 kWh of electricity a year, which is about £658 in units at 26.32p. A single heater used every day in winter can add a large share of that on its own.
Kettles
A kettle is one of the most powerful things in a home, usually 2,500 to 3,000 watts, but it only runs for a few minutes. A 3kW kettle costs about 1.3p a minute, so a 3-minute boil costs about 4p.
The biggest saving is boiling only the water you need. Boiling a full kettle for one mug heats water you then let go cold. Descaling helps too, as scale slows the element down.
Air fryer, oven, microwave and hob
An air fryer is smaller and heats up quickly, so it usually costs less than a full-size oven for the same food. With typical figures, a 20-minute air fryer meal costs about 13p and a 45-minute oven meal about 28p. Once a day for a year, that is a saving of about £55.72.
- Power
- 1,500 W
- Time
- 20 min
- Each meal
- 13p
- A year, daily
- £48.03
- Power
- 2,400 W
- Time
- 45 min, on 60%
- Each meal
- 28p
- A year, daily
- £103.75
The gap closes when you fill the oven: one oven cooking a whole family meal can beat several air fryer batches. A microwave is the cheapest way to reheat food, at about 3p for 5 minutes. A slow cooker uses little power (about 200 watts) but runs for hours, so 8 hours costs about 42p. One ring of an electric hob for 20 minutes costs about 9p.
Washing and drying clothes
A washing machine spends most of its energy heating water. A typical 40°C wash uses about 0.75 kWh, or 20p. Washing at 30°C or on an eco programme uses less.
Drying is the expensive part. A vented or condenser tumble dryer at 2,500 watts for 75 minutes uses about 3.1 kWh, or 82p a load. A heat pump dryer recycles its warm air and uses about half as much: about 42p a load. At three loads a week, that is £128.66 a year against £65.88.
A heated clothes airer at 300 watts for 4 hours costs about 32p. A dehumidifier in the same room for 8 hours costs about 63p, but also helps with damp. Drying outside is free.
Electric heaters
Every electric heater turns one unit of electricity into one unit of heat, whatever its type. A 2kW fan heater and a 2kW convector give the same heat for the same cost: about 53p an hour at full power, or £1.58 for 3 hours.
An oil-filled radiator holds its heat and its thermostat switches the element off once the room is warm. At 1,500 watts, drawing power about 60% of the time, 4 hours costs about 95p. A halogen heater warms people in front of it quickly, which suits short spells: 1,200 watts for 3 hours also costs about 95p.
Heaters add up quickly
A 2kW heater used for 3 hours every day costs about £48 a month. Over a whole year that is £576.41, nearly as much as the unit cost of a typical home’s other electricity.
Electric heater or gas central heating?
Gas is much cheaper per unit than electricity. At the October to December 2026 cap, gas costs 7.97p per kWh. A boiler loses some heat up the flue: new gas boilers in England must be rated at least 92% efficient, and we assume 90% in real use. That makes a unit of heat from gas about 8.86p, against 26.32p from an electric heater: electric heat costs about 3 times as much.
- Heat a day
- 6 kWh
- Cost a day
- £1.58
- A year, daily
- £576.41
- Same heat a day
- 6 kWh
- Cost a day
- 53p
- A year, daily
- £193.94
That is not the whole story. Central heating warms every room with a radiator, while a heater warms one. If you only need one room warm for a few hours, a heater can cost less than heating the whole house. Choose “Gas central heating” in the calculator to compare your own heater.
Electric showers and immersion heaters
An electric shower is often the most powerful appliance in a home: 8.5 to 10.5kW is common. A 9.5kW shower costs about 4p a minute, so an 8-minute shower is about 33p and a 10-minute one about 42p. Four people each showering for 8 minutes every day would spend about £486.74 a year.
An immersion heater heats a tank of hot water. A 3kW element running for an hour costs about 79p, or £288.20 a year if used daily. A timer, a well-insulated tank and an off-peak rate all cut that cost.
Fridges and freezers
A fridge freezer runs all day, every day, but its compressor only draws power part of the time. An average draw of about 30 watts works out at about 263 kWh a year, or £69.17.
The energy label gives a better figure for your own model: it shows the kWh used a year. Multiply that by your unit rate. Older models, frost-covered freezers and a fridge next to an oven or in a warm garage all use more.
TVs, consoles and computers
Screens use less than people expect. A 100-watt TV on for 4 hours a day costs about 11p a day, or £38.43 a year. A games console at 150 watts for 2 hours a day costs about 8p a day, or £28.82 a year. A laptop uses little power, about 8p for 6 hours, while a desktop computer and screen at 200 watts costs about 21p for 4 hours, or £76.85 a year.
Larger TVs and gaming PCs draw more. The figure on the rating plate is the most it can draw; average use is often lower.
Standby power
Things left on standby still use a little power. Each watt drawn all year round costs about £2.31 at 26.32p a unit. A home with 10 watts of standby across a TV, a set-top box, chargers and a microwave clock spends about £23.06 a year on nothing.
Switching off at the wall, or using a plug with a timer, removes that cost. Leave fridges, freezers and anything that needs to stay on alone.
Charging an electric car at home
A typical home charger delivers about 7kW. Four hours puts about 28 kWh into the battery, which costs about £7.37 at the price cap rate. On an overnight tariff at 8p a unit, the same charge costs about £2.24. Twice a week for a year, that is £768.54 against £233.60.
To compare an electric car with petrol or diesel over several years, use our petrol vs electric car calculator.
Economy 7 and off-peak rates
Economy 7 tariffs have two rates: a cheaper rate for seven hours at night and a dearer rate for the rest of the day. Ofgem assumes 42% of an Economy 7 home’s electricity is used at night. Smart tariffs with cheap overnight or off-peak periods work in a similar way.
A cheap night rate only saves money if you move use into those hours: a dishwasher, washing machine or car charger on a timer, or a hot water tank heated overnight. If most of your use is in the day, the higher day rate can make Economy 7 cost more than a single-rate tariff.
Pick “Off-peak” under More options in the calculator and enter the night rate from your bill.
Finding the wattage and energy label
The power is printed on the rating plate, usually on the back, underneath or inside the door, and in the manual. It is shown in watts (W) or kilowatts (kW). If it shows a range, such as 2,520 to 3,000W, the higher figure is the most it can draw.
The energy label on newer appliances gives energy use in a more useful form:
- Fridges and freezers: kWh a year.
- Washing machines, washer-dryers and dishwashers: kWh per 100 cycles on the eco programme. Divide by 100 for one cycle.
- TVs and monitors: kWh per 1,000 hours. Divide by 1,000 for one hour.
Measuring real use
A plug-in energy monitor sits between the socket and the appliance and shows the power it actually draws and the units used. It is the most accurate way to see what a thermostat appliance, such as a fridge or oil-filled radiator, really uses over a day.
A smart meter’s in-home display shows what the whole home is using right now. Switch an appliance on and watch the jump: that is roughly its power.
Cutting the cost
- Use it for less time. Cost rises in step with time, so halving the time halves the cost.
- Pick the smaller tool. A microwave or air fryer for small meals, a heated airer instead of a tumble dryer.
- Use lower settings. Washing at 30°C, eco programmes and a lower heater setting all use less.
- Move use to cheaper hours if you have an off-peak tariff.
- Check your tariff. See your whole bill with our energy bill calculator.
If you are struggling to pay, contact your supplier: they must offer help such as a payment plan. Our benefits checker shows support you may be missing, and people over State Pension age can check Pension Credit, which opens the door to other help with bills. If you are moving home, add energy to your moving house budget.