How many infrared panels do I need?
Panel sizing is where most infrared installations go wrong, in both directions. Undersize and the room never reaches temperature on the coldest days; oversize and you pay for output that cycles off. The arithmetic is simple enough to sanity-check any quote you are given.
How many infrared panels does a room need?
As a starting point, allow roughly 60 to 70 watts per square metre for a well-insulated room, 80 to 100 for average UK housing stock, and 100 to 130 for solid walls, large glazing or a room above an unheated space. Divide the total by the panel wattage to get the number of panels, then check the ceiling height and mounting positions, because output has to reach the occupied zone.
The sizing arithmetic
Multiply the floor area in square metres by the watts per square metre band that matches the room's insulation. A 16 square metre bedroom in an average-insulation house needs roughly 1,280 to 1,600 watts, which is typically two 700 watt panels or one 1,200 watt panel plus margin.
Two adjustments matter. Ceilings above about 2.7 metres increase the requirement because there is more volume and a longer distance from panel to occupant. Rooms with more than about 25% of the wall area in glazing need the upper end of the band, or the glazing dealt with first.
Worked examples
A 12 square metre home office, well insulated, modern build: around 780 watts, so one 800 watt ceiling panel. A 20 square metre living room in a 1930s semi with solid walls: around 2,000 to 2,400 watts, so two 1,200 watt panels on separate zones. A 6 square metre bathroom: around 500 to 600 watts, usually a single mirror panel rated for the zone.
A 30 square metre village hall side room used two evenings a week: size for the heat loss as above, but prioritise fast radiant response over reaching a steady air temperature, because the building will never get there in two hours.
What a rule of thumb cannot tell you
Watts per square metre is a sanity check, not a design. A proper assessment calculates heat loss from wall, roof, floor and glazing U-values, air-change rates and the target temperature, and it also confirms the incoming electrical supply can carry the total load once every panel runs at once.
It also decides mounting: ceiling panels give even coverage and free wall space but need clearance above people, while wall panels suit lower ceilings and need a clear line of sight to the occupied zone. Furniture blocking a panel wastes output completely.
A sensible shortlist
- Measure floor area and ceiling height before comparing any quote.
- Pick the watts-per-square-metre band from the actual insulation, not the build year alone.
- Add margin for large glazing or rooms above unheated spaces.
- Check the total load against the incoming electrical supply capacity.
- Confirm nothing will block the line of sight between panel and occupants.
- Ask for a heat-loss calculation on anything larger than a single room.
Frequently asked questions
Reviewed by the Infrared Heat Solutions technical team · Last updated July 2026 · Data sources: Ofgem price cap, Energy Saving Trust, first-party running-cost model