This article provides general information. Equipment, capacity and fault decisions should consider the site and current manufacturer documentation.
Floor area is only the starting point
Room area provides an initial comparison, but ceiling height, solar gain, insulation, occupancy and heat-producing equipment can all change the required load.
Consider orientation and solar gain
A south- or west-facing room exposed to strong afternoon sun may have a different cooling load from an equally sized shaded room. Large glazed areas can increase that load.
Review insulation and windows
Wall and roof insulation, frame condition, glazing and uncontrolled air leakage affect heat gain. A final capacity should therefore not be selected from floor area alone.
Include occupancy and usage
Homes, offices, shops and cafés have different schedules and internal loads. People, lighting and equipment that operate continuously must be included in the assessment.
Confirm the result with a site survey
An estimate is useful for pre-selection. The final system and capacity must also consider indoor and outdoor unit positions, pipework, drainage and electrical conditions.