Tools
Infrared heater sizing calculator
A transparent planning estimate: area, exposure, mounting height and climate in — wattage and a model recommendation out.
Short answer: Multiply the heated area by 90 W/m² for a sheltered space, 120 W/m² for a semi-open space or 150 W/m² for an exposed one, then adjust for mounting height and climate. A 30 m² semi-open terrace in a temperate climate works out at about 3.6 kW, or two 1.8 kW heaters.
Estimate your space
Planning estimate only. Wind protection, glazing and occupancy change the real requirement — confirm the layout with our team before ordering.
View 13B 1.8 kWWorked examples
| Space | Result |
|---|---|
| Covered restaurant terrace, 30 m², temperate | 3.6 kW total — two 1.8 kW units or one 3.2 kW unit plus one 1.0 kW unit |
| Open rooftop deck, 40 m², cold | 6.9 kW total — two to three 3.2 kW units, with windbreaks specified first |
| Hotel breakfast courtyard, 25 m², sheltered, mild | 2.0 kW total — one 2.2 kW unit, zoned separately from the indoor room |
| Warehouse packing bench, one position | 1.0–1.8 kW per position — spot heating, not whole-building heating |
How the calculation works
The estimate uses the same shorthand specifiers use in a first-pass layout: a base intensity per square metre, adjusted for how exposed the space is, how high the heaters are mounted, and how cold the winter is.
Output (W) = area (m²) × base W/m² × height factor × climate factor
- Base intensity: 90 W/m² sheltered, 120 W/m² semi-open, 150 W/m² exposed.
- Height factor: 1.0 at 1.8–2.5 m, 1.1 at 2.5–3.0 m, 1.2 above 3.0 m.
- Climate factor: 0.9 mild, 1.0 temperate, 1.15 cold.
- Unit count: total output divided by the selected model, rounded up.
These coefficients are planning conventions, not a substitute for a heat-loss calculation. For a commercial project with a specification requirement, ask for a designed layout — we will produce one from your plan.
Frequently asked questions
How is the recommended output calculated?
Output = area × base watts per m² (90 sheltered, 120 semi-open, 150 open) × height factor (1.0 up to 2.5 m mounting, 1.1 to 3 m, 1.2 above 3 m) × climate factor (0.9 mild, 1.0 temperate, 1.15 cold). The result is rounded up to the nearest available model combination.
Why does the calculator ask about height?
Radiant intensity falls with distance from the element. A heater mounted at 3 m delivers less to a seated guest than the same unit at 2 m, so the required output rises with mounting height. We recommend 1.8–2.5 m where the architecture allows it.
Is the result a guaranteed specification?
No — it is a planning estimate. Wind, open boundaries, glazing, ceiling height and occupancy pattern can move the requirement by 20–30%. Use it to size a budget and a circuit plan, then confirm the layout with our team against a drawing.
What if the calculator recommends more than six units?
Past six units the layout usually needs zoning and a proper distribution board rather than more heaters on one circuit. Send us the plan: at that scale a designed layout is more reliable than a per-unit calculation.
Want the calculation checked?
Send the plan with the seated area and mounting surfaces marked. We will confirm the output, the zoning and the electrical load.
Ask our team