How it is calculated
- Base: about 20 BTU per square foot (≈ 215 BTU per m²) in a moderate climate.
- Sunny room +10%, shaded −10%.
- +600 BTU per person above two, +4,000 BTU for a kitchen.
- Very hot climates (the Gulf, southern Morocco in summer) +30% or more.
One ton = 12,000 BTU. Common sizes: 9,000, 12,000, 18,000, 24,000 and 30,000 BTU.
Worked example
A 4 × 4 m (16 m²) sunny bedroom for two in a hot climate: 16 × 215 = 3,440 × 1.1 × 1.3 ≈ 4,920 BTU, so the nearest unit is 9,000 BTU (¾ ton).
Frequently asked questions
Is bigger always better?
No — an oversized unit cools fast, cycles often, dehumidifies poorly and wastes power.
High ceilings?
Above 3 m, scale up roughly by ceiling height ÷ 2.5 m.
Inverter vs fixed-speed?
Inverters vary compressor speed and usually save 30–50% electricity.