How the estimate is built
The calculator starts from room floor area and a room-type watts-per-square-metre allowance, then adjusts for ceiling height and the heat-gain factors you select. Results are shown in kilowatts and approximate BTU per hour for comparison with product descriptions.
It is intentionally conservative about certainty. Solar gain, fabric, ventilation, occupancy and simultaneous use can outweigh floor area. A surveyed heat-load calculation should replace this estimate before equipment is ordered.
What this does not cover
- Whole-house multi-room diversity or multi-split shared capacity
- Commercial extract-dominated kitchens or process cooling
- Server rooms and IT cupboards. Use the server room calculator for continuous IT loads
- A guarantee that a named model will meet design conditions
Read the capacity selection guide, then estimate installation cost once the rooms are clear.