What Size Electric Heater Do I Need? Wattage by Room Size
What size electric heater do I need?
One simple sum answers it: room area multiplied by the right watts per square metre. This guide gives you the rule, a full wattage table from 400W to 2000W, and worked examples for bedrooms, living rooms and conservatories.
Multiply your room area by watts per square metre.
For a typical insulated room with a standard ceiling height, allow 80W per square metre of floor area. So a 10 square metre room needs 10 x 80 = 800W of heating.
Adjust the figure for the room itself. In a well insulated space, a modern build with double glazing and good loft insulation, 60W per square metre is often enough. In a conservatory, a poorly insulated room, or anywhere with high ceilings or large areas of glass, allow 130W per square metre or more, because heat escapes faster than the average room.
Once you have your figure, round up to the next available output. A thermostat means a slightly larger heater simply reaches temperature sooner and then cycles off, while an undersized heater runs flat out and never quite gets there. When in doubt, size up.
Room size to wattage, at a glance.
Find your room size, pick the column that matches your insulation, and the table gives you the wattage. Every figure links to the heaters of that output.
| Room size | Well insulated new build (60W per m2) | Typical (80W per m2) | Conservatory or poor insulation (130W per m2) |
|---|---|---|---|
| 5 m2 (box room, home office) | 400W | 400W | 750W |
| 8 m2 (single bedroom) | 500W | 750W | 1200W |
| 10 m2 (double bedroom) | 600W | 800W | 1400W |
| 12 m2 (large bedroom, kitchen) | 750W | 1000W | 2000W |
| 15 m2 (average living room) | 1000W | 1200W | 2000W |
| 20 m2 (large living room) | 1200W | 2000W | 2 x 1400W |
| 25 m2 (open plan space) | 1500W | 2000W | 2 x 2000W |
Figures are rounded up to the nearest stocked output. For example, 8 m2 at 130W per m2 comes to 1040W, so the table recommends a 1200W heater rather than a 1000W model that would fall short. Browse the full range of electric heaters and electric radiators to compare every output side by side.
Three rooms, three sums.
750W
A typical single bedroom needs about 640W, so round up to the next stocked size. A quiet wall mounted panel from the 750W electric heaters range, set on a timer, warms the room before bed and switches itself off overnight.
2000W
A large living room needs about 1600W, so one 2000W heater gives comfortable headroom. Fit one heater from the 2000W electric heaters range, or split the load across two 800W heaters for more even warmth.
1500W+
All that glazing loses heat fast, so a 12 m2 conservatory needs at least 1560W. Start at the 1500W electric heaters and step up to 2000W if the room is exposed or north facing.
When to split the wattage across two heaters.
Long or L-shaped rooms
A single heater at one end of a long room leaves the far end cold. Two smaller units on opposite walls spread the warmth evenly, with no cold corners. In an L-shaped room, one heater per leg is almost always the better layout.
Rooms over 20 m2
Above 20 square metres a single 2000W wall mounted heater is often working at its limit, especially with average insulation. Two mid-size units, for example a pair from the 1000W electric heaters or 1200W electric heaters ranges, reach temperature faster and hold it more steadily.
Running costs stay the same
Two 1000W heaters draw the same power as one 2000W heater, so splitting costs nothing extra to run. Each unit has its own thermostat, so you can zone the room: full warmth by the sofa, a lower setting by the dining table. WiFi models such as the ADAX NEO WiFi wall heater (£130.20) can be scheduled together from one app.
The right heater for each room.
The sum gives you the wattage. The room decides the type. A bedroom wants silence, a conservatory wants extra output and frost protection, and a workshop wants heat you can feel the moment it switches on.
Wall mounted panel heaters in the 1000W and 2000W sizes are our most popular all-rounders, slimline, flat against the wall and controlled by a thermostat and timer. Prices start at £70.00 for the Vitra WiFi electric panel heater, which can be wall mounted or used freestanding.
Bedrooms
Choose a quiet convector panel with a thermostat and timer: no fan, no noise, just gentle circulating warmth that pre-heats the room and drops away overnight. The ADAX Neo Black panel heater (£81.67 on sale) and the ADAX VP12 with Bluetooth app (£91.00) are both popular bedroom heaters, and the clearance ADAX FAMN WiFi (£64.99) is the budget route to app control.
Living rooms and large rooms
The best electric heater for a large room is either one 1500W to 2000W unit or a split pair, sized by the table above. WiFi models such as the Vitra Verde WiFi (£137.70, Lot 20 compliant) and the SolAire LYNDO WiFi (£136.00) let you schedule heat around the hours you actually use the room.
Kitchens
A wall mounted panel keeps the floor clear and sits well above splash level. Keep any heater out of the sink area, and note that models rated IPX4, like the ADAX NEO WiFi, are built to shrug off the damp air of a busy kitchen.
Conservatories and glass rooms
Glazing leaks heat, so use 130W per m2 or more and pick a heater with a frost protection setting to guard plants and pipework on cold nights. Radiant panels such as the Radialight Kyoto Dual Therm work well here because they warm people and surfaces directly rather than the air escaping through the glass.
Garages, workshops and sheds
Draughty spaces lose warm air quickly, so radiant heat you can feel immediately beats slow convection. Consider a radiant panel such as the Radialight Aetherea Dual Therm (£217.80), or a freestanding unit like the portable ADAX Neo (£169.00) that moves with you between jobs.
Static caravans and holiday lets
Wall mounted electric radiators suit static caravans well: no boiler, no pipework, sized by the same watts per m2 rule. Choose thermostatic models you can leave on a low frost setting between visits, and check the total load your consumer unit can supply before fitting several heaters.
Wattage questions, answered.
What size room will a 1000W electric heater heat?
A 1000W heater comfortably heats a typical insulated room of up to 12 m2 (12 x 80 = 960W), or up to 16 m2 in a well insulated new build. That covers most double bedrooms, home offices and small kitchens.
Is a 2000W electric heater enough for a large room?
Yes, for most. A 2000W wall mounted heater handles a typical room of up to 25 m2 (25 x 80 = 2000W), or over 30 m2 in a well insulated new build. Beyond that, or in a poorly insulated space, split the load across two heaters for even warmth.
What size electric heater do I need for a bedroom?
A single bedroom of around 8 m2 needs about 640W, so a 750W model covers it. A double bedroom of 10 to 12 m2 needs 800W to 1000W. Pick a silent convector panel with a thermostat and timer so it warms the room before bed and switches off while you sleep.
What is the best electric heating for a conservatory?
A wall mounted electric panel or radiant heater sized at 130W or more per square metre, so a 12 m2 conservatory needs at least 1560W: choose 1500W as a minimum and 2000W if it is exposed. A frost protection setting is worth having to protect plants and pipework overnight.
Does a bigger heater cost more to run?
Not in practice, if it is thermostatically controlled. A correctly sized or slightly larger heater reaches temperature and cycles off, while an undersized one runs continuously at full power without ever getting the room warm. Sizing up modestly is the efficient choice.
Can I use a wall mounted electric heater in a static caravan?
Yes. Electric radiators are a popular central heating alternative in static caravans because they need no boiler or pipework. Size them with the same watts per m2 rule, use the frost setting when the caravan is empty, and have an electrician confirm the supply can carry the total load. Call 01325 717 899 if you would like help choosing.
Sized it? Every output is in stock.
From 400W panels to 2000W radiators, every heater comes with free next working day delivery to mainland UK and the Isle of Man. Explore more advice in our full library of buying guides, including Convector Heaters Explained and Bathroom Heating: What Is Safe and What Works.
Shop All Electric Heaters