A 30 m² room needs about 6,458 BTU/h of cooling and 7,984 BTU/h of heating; a 500 sq ft room needs about 10,000 BTU/h of cooling.
- Cooling (BTU/h)
- Heating (BTU/h)
| Room area (m²) | Cooling (BTU/h) | Heating (BTU/h) |
|---|---|---|
| 10 | 2,153 | 2,661 |
| 15 | 3,229 | 3,992 |
| 20 | 4,306 | 5,323 |
| 25 | 5,382 | 6,654 |
| 30 | 6,458 | 7,984 |
| 35 | 7,535 | 9,315 |
| 40 | 8,611 | 10,646 |
| 45 | 9,688 | 11,977 |
| 50 | 10,764 | 13,307 |
| 55 | 11,840 | 14,638 |
| 60 | 12,917 | 15,969 |
| 65 | 13,993 | 17,300 |
| 70 | 15,069 | 18,630 |
| 75 | 16,146 | 19,961 |
| 80 | 17,222 | 21,292 |
How it is computed
Cooling = floor area in sq ft × 20 BTU/h, the common sizing rule for one occupant and average sun. Heating = room volume (2.5 m ceiling) × 1.2 W/m³·K × 26 K (21 °C inside, −5 °C outside), converted to BTU/h. Add 600 BTU/h per extra occupant and about 10% for a sunny room.
FAQ
Is a bigger air conditioner better?+
No. An oversized unit cycles on and off before removing humidity, which leaves the room cold and clammy.
Why is my heating need higher than the table?+
Older windows, poor insulation or a colder design temperature raise the load. Enter your own values in the heating load calculator.