Electric Heater Running Cost Calculator
Works out the monthly and seasonal running cost of a fan heater, oil-filled radiator or panel heater from its power rating and hours of use.
A 2 kW electric heater running 5 hours a day for 20 days uses 200 kWh in a month. Multiply that figure by the unit rate on your electricity bill to get the monthly running cost, and by the number of winter months to get the season total. Resistance heaters turn effectively all the electricity they draw into heat, so the kWh figure is the energy that reaches the room, with no efficiency factor to apply.
In the UK, electric heating is common in flats, bedsits and older homes without a gas connection, and it is often used to warm a single room. The running cost is easy to underestimate. In a two-bed flat in Glasgow, for example, a fan heater in the living room and an oil-filled radiator in the bedroom can add up quickly across a cold winter. Each heater draws its full rated power for every hour it runs, whatever the room temperature, so a 1.5 kW fan heater uses 1.5 kWh each hour.
Heat pumps work differently. They move heat from the outside air rather than generating it from electricity alone, so one unit of electricity can deliver several units of heat. For a home that needs heat for much of the day, the choice of heating system therefore matters more than the choice of heater. This calculator does not compare systems. It converts the power rating and usage pattern you enter into an estimate of the cost on your bill, so you can see what a single heater, or two, contributes.
The result is an estimate, not a bill forecast. It assumes the heater runs for the hours you enter, at its rated power, on every day you enter. Real use is often lower, because a thermostat switches the element off once the room reaches the set temperature. The explanation below covers how the energy use is calculated, where the figures come from, and the common mistakes that push a bill higher.
The explanation below uses metric units; the calculator works in either system.
The result updates automatically.
Fast heat-up with forced convection. Typical models: 750 W–2,000 W.
Shown on the appliance's label. E.g. 1,500 W = 1.5 kW.
Average running time. In homes without central heating, 4–8 h/day is common in winter.
In December and January, count 25–30 days. In milder months (October, March), use fewer.
Unit rates vary by tariff, meter type and supplier, and the standing charge is billed separately. Check the figures on your own electricity bill. Ofgem publishes general guidance on energy tariffs and bills.
Estimated monthly cost
usage: 150.0 kWh/month
- Usage per hour
- 1.5 kWh
- Cost per hour
- £0.33
- Daily usage
- 7.5 kWh
- Monthly usage
- 150.0 kWh
- Seasonal cost (5 winter months)
- £165.00
How it works
Formula
How the calculation works
Electric Heater Running Cost in the UK: How It Is Calculated
Electric heaters are a common way to warm a flat, a bedsit, a single room or a home without a gas connection. Their running cost is simple to work out, and it is often higher than people expect. A 2 kW heater running for 6 hours a day over 30 days uses 360 kWh. Multiply that figure by the price per kWh on your electricity bill to find the monthly cost of that one appliance.
How the energy use is calculated
Resistance heating is simple physics. An electric element converts effectively all of the electricity it draws into heat, so there is no coefficient of performance to apply and no transmission loss to add back. The energy used is the rated power, in kilowatts, multiplied by the hours the heater runs. The result is measured in kilowatt-hours (kWh), the unit that appears on your electricity bill.
The calculator applies three steps in sequence:
- Daily energy use (kWh) = rated power (kW) × hours of use per day
- Monthly energy use (kWh) = daily energy use (kWh) × days of use per month
- Cost = monthly energy use (kWh) × price per kWh
As a worked example, a 1 kW quartz heater run for 4 hours a day on 20 days uses 4 kWh a day and 80 kWh a month. Because the cost rises in direct proportion to each input, doubling the hours doubles the monthly figure, and two heaters in different rooms double it again.
Your electricity bill shows a unit rate for each kWh and a standing charge. The standing charge is paid whether or not you use the heater, so it is not included in this calculator. Compare the result only with the unit-rate part of your bill.
Thermostats and running time
Many heaters have a built-in thermostat. When the room reaches the set temperature, the element switches off and the heater uses no power until the room cools. The power drawn while the element is on is still the full rated power. A thermostat therefore reduces the number of hours the heater actually runs, not the power it draws when running.
How much time a thermostat saves depends on the outside temperature, the insulation of the room and the size of the space. A well-insulated room on a mild day may need very little running time, while a draughty room on a cold night may need almost continuous running. The calculator cannot know these conditions, so for a more realistic estimate enter the hours the heater runs, not the hours it is switched on.
Types of electric heater in the UK
Four main types of resistance heater are sold for home use. Each has a different typical power range and suits different situations.
| Type | Typical rated power | Best use |
|---|---|---|
| Fan heater | 750 W to 2,000 W | Quick warm-up of a small room |
| Halogen or quartz heater | 800 W to 2,400 W | Direct warmth for a specific spot |
| Oil-filled radiator | 750 W to 2,500 W | Steady background heat in a medium room |
| Panel heater | 500 W to 2,000 W | Fixed installation in a living room or bedroom |
A fan heater warms the air quickly but holds little heat, so the room cools soon after it is switched off. An oil-filled radiator takes longer to warm up, but the oil keeps releasing heat after the element is switched off, which can shorten the time it needs to run. Panel heaters are usually fixed to a wall and suit rooms that are occupied for several hours at a stretch. Whatever the type, the cost per kWh is the same, because all of them convert electricity to heat at the same rate. The difference lies in how quickly the room warms and how long it stays warm.
Check the rated power on the label or in the manual before entering it, since every result in this calculator depends on that single figure.
Seasonal cost over the winter
Take a two-bed flat in Glasgow with two 1.5 kW heaters, one in the living room and one in the bedroom, each running 5 hours a day on 22 days a month:
- Monthly energy use: 2 × 1.5 kW × 5 h × 22 days = 330 kWh
- Monthly cost: 330 kWh × your price per kWh
- Five-month winter total: 330 kWh × 5 months = 1,650 kWh, multiplied by your price per kWh
This figure often surprises households, because each heater feels like a small addition to the bill when it is switched on for only a few hours. For comparison, a heat pump with an efficiency of 3.5, meaning 3.5 units of heat for each unit of electricity, would deliver the same heat from about 94 kWh a month. This is illustrative arithmetic. Real heat pump performance depends on the design, the outside temperature and how the system is installed.
Common mistakes and how to keep the bill down
The most frequent mistake is setting the heater to its highest setting and then opening a window because the room has become too warm. Each time a window is opened on a cold morning, the heat built up in the room leaves with the air, and the heater must then replace it. Keeping the room at a lower temperature and wearing warmer clothes uses less energy than heating a room that is then cooled by ventilation.
The World Health Organization's housing and health guidelines recommend an indoor temperature of at least 18 °C. A thermostat set well above that level keeps the heater running for longer, so the setting has a direct effect on the hours in your calculation. Choose the lowest temperature that keeps the room comfortable, and check whether the thermostat is accurate by comparing it with a separate room thermometer.
Oil-filled radiators need time to warm up. Switching one on shortly before you need it is more efficient than leaving it on all day in an empty room. Heating an unoccupied room is a common source of unnecessary use, so set a timer or switch the heater off when you leave.
Finally, draughts and gaps around doors and windows let warm air escape. Sealing them and closing curtains at dusk reduces the heat the heater must supply, which in turn reduces the hours it needs to run.
When an electric heater is not the right solution
The main limitation of direct electric heating is the cost of each unit of heat it produces. Every unit of heat costs one unit of electricity, which tends to be a costly way to heat a whole home. The Energy Performance Certificate (EPC) rating of a home reflects this. The SAP methodology used to calculate EPCs treats electricity as a more expensive and higher-impact fuel than gas, so a home that relies heavily on direct electric heating tends to score lower than one with an efficient heat pump.
Building standards differ across the UK. England and Wales use the Building Regulations and their Approved Documents, and Approved Document Part L sets energy efficiency requirements for new work and some alterations. Scotland uses the Building (Scotland) Regulations. Electrical work in homes in England and Wales falls under Part P of the Building Regulations, so a new fixed heater or circuit should be installed by a competent person registered under a Part P scheme, or notified to building control.
For whole-home heating, an air source heat pump is generally the more efficient option. Heat pump installers should be certified under the Microgeneration Certification Scheme (MCS), which sets the quality standard for these installations. The difference in running cost over a heating season can be large for a typical household, so it is worth requesting quotes and comparing running costs on a like-for-like basis before deciding.
Electric heaters suit occasional use: a spare room, a utility room, a home office used for a few hours a week, or a top-up on a particularly cold day. For regular heating of a whole home, the seasonal figure from this calculator is a sound reason to compare the alternatives.
How to read the result
The monthly figure is the one to compare with your bill, since most bills are issued monthly or quarterly. The hourly figure shows how much a single hour of use adds, which helps when you are deciding whether to run a heater in an empty room. The seasonal figure multiplies the monthly figure across five winter months, so it is a planning figure rather than a forecast.
Limits of this calculator
The calculator uses the rated power and the hours and days you enter. It does not include the standing charge, the thermostat cycle, the outside temperature, the insulation of your home or any change of tariff during the year. Use it to compare scenarios, such as one heater against two, or four hours a day against six, rather than as an exact forecast. Ofgem, the energy regulator for Great Britain, publishes information about how energy tariffs and bills work, but the unit rate that applies to you is the one shown on your own bill.
The result is only as good as the inputs. Check the rated power on the label, use the hours the heater actually runs and confirm the unit rate on your bill before relying on the figures.
Frequently asked questions
How much does a 2 kW electric heater cost to run for one hour?
A 2 kW heater uses 2 kWh for every hour it runs at full power. To get the cost of that hour, multiply 2 kWh by the price per kWh shown on your electricity bill. If it runs for 5 hours a day over 20 days, it uses 200 kWh in a month, so the monthly cost is 200 kWh multiplied by your unit rate. The standing charge on your bill is not included in this figure, and it is paid whether or not you use the heater.
Which electric heater uses the least electricity?
All electric resistance heaters convert effectively all the electricity they draw into heat, so no type is more efficient than another in that sense. What changes the bill is the rated power and how long the heater runs. A lower-powered heater costs less per hour, but it may take longer to warm the room, so the total can be similar. A higher-powered fan heater can warm a small room more quickly and then be switched off. A built-in thermostat helps by switching the element off when the room reaches the set temperature, so it is worth choosing a model that has one.
How much electricity does a 1,500 W heater use in a month?
It depends on how many hours and days it runs. At 4 hours a day for 20 days, a 1.5 kW heater uses 1.5 × 4 × 20 = 120 kWh. At 6 hours a day for 25 days, typical of heavy use in January, it uses 225 kWh. Find your unit rate on your electricity bill and multiply the kWh figure by it to get the cost. The calculator does this automatically once you enter the hours and days.
Is an electric heater cheaper to run than heat pump heating?
Per unit of heat, a heat pump is usually cheaper to run, because it moves heat from the outside air rather than generating it from electricity alone. An electric heater produces one unit of heat for each unit of electricity, while a heat pump can deliver several units of heat for the same electricity. Installation costs for a heat pump are much higher, and performance can fall in very cold weather, so the right answer depends on the home and how much heat it needs. A heat pump is generally the better choice for regular heating of a whole home.
Does a thermostat reduce the electricity an electric heater uses?
Yes, but only through the time it runs. A thermostat switches the element off once the room reaches the set temperature, so the heater uses no power during those periods. While the element is on, the heater draws its full rated power, so a 2 kW heater still uses 2 kWh for each hour it runs. How much time a thermostat saves depends on the outside temperature, the insulation of the room and the set temperature, so the actual running time can be well below the hours the heater is switched on.
What temperature should I set my electric heater to?
The World Health Organization's housing and health guidelines recommend an indoor temperature of at least 18 °C. A higher setting uses more energy, because the heater runs for longer to reach it. Each degree above what you need adds to the running time, so it is worth setting the thermostat to the lowest temperature that keeps you comfortable and wearing warmer clothes rather than turning the heat up. Your local council may also offer free or low-cost home energy advice.
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By RivoCalc · Reviewed under our editorial methodology · Updated 3 June 2026
These figures are estimates based on the rated power and the hours and days you enter. Real energy use varies with the heater's thermostat, the size and insulation of the room, the outside temperature and how long the heater actually runs. Check your own electricity bill for the unit rate and any standing charge, and treat the result as a guide rather than a forecast of your bill.