How Many BTUs Do You Need? Room-by-Room Sizing Guide
MeacoCool MC Series Pro 9,000 BTU
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Buying an undersized air conditioner is the most common mistake — and the most expensive. A unit that's too small runs continuously, never reaches the set temperature, and wears out faster. Here's exactly what BTU you need for every room type.
Quick Reference Table
| Room | Typical Size | Min BTU | Recommended |
|---|---|---|---|
| Small bedroom | 9-12 m² | 5,000 | 7,000 |
| Master bedroom | 14-18 m² | 7,000 | 9,000 |
| Living room | 18-25 m² | 9,000 | 12,000 |
| Open-plan living/kitchen | 25-35 m² | 12,000 | 14,000 |
| Home office | 8-12 m² | 5,000 | 7,000 |
| Kitchen | 10-15 m² | 8,000 | 10,000 |
| Conservatory | 12-18 m² | 10,000 | 14,000 |
| Garage/gym | 15-20 m² | 9,000 | 12,000 |
The BTU Formula for UK Homes
Look at the kit — then buy it
Pro Breeze 12,000 BTU 4-in-1 Smart AC
AuraHome Portable AC 9,000 BTU — 4-in-1 Cool/Dehumidify/Fan
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Start with 340 BTU per square metre for a standard UK room with 2.4m ceilings. Then adjust:
- +10% if the room faces south or west (direct afternoon sun)
- +10% for each additional person regularly in the room
- +15% if it's a kitchen (appliances generate heat)
- +20% for conservatories or rooms with large windows
- +15% if ceiling is higher than 2.4m
- -10% if the room faces north and is well-shaded
Example: Master Bedroom (16m²)
Base: 16 × 340 = 5,440 BTU
South-facing (+10%) → 5,984
Two people (+10%) → 6,582
Standard ceiling → no adjustment
Final recommendation: 7,000-9,000 BTU
Common Sizing Mistakes
❌ Buying Too Small
A 5,000 BTU unit in a 20m² living room will run flat-out, never cool the room, and burn out in 2 years. The compressor never cycles off — it just runs until it dies.
❌ Buying Too Large
A 14,000 BTU unit in a small bedroom will short-cycle — blasting cold air for 3 minutes, shutting off, then restarting. This is inefficient, noisy, and doesn't dehumidify properly.
❌ Ignoring Heat Sources
A kitchen with an oven, fridge, and dishwasher generates far more heat than a bedroom. A conservatory with floor-to-ceiling glass is a greenhouse. Size up accordingly.
Golden rule:
When in doubt, size up by one step. A slightly oversized unit will still cycle properly in UK temperatures (we rarely hit 40°C). An undersized unit is useless on the one day you actually need it — the heatwave.