How to Calculate the BTU Your Space Needs
Avoid buying an undersized or oversized unit.
Quick reference table
This table is a general guide; the exact size depends on your space's specific conditions.
- 9,000 BTU: up to 12 m² (small bedroom)
- 12,000 BTU: up to 18 m² (bedroom, small office)
- 18,000 BTU: up to 26 m² (medium living room)
- 24,000 BTU: up to 35 m² (large living room, dining area)
- 32,000 BTU: up to 46 m² (open spaces, small commercial units)
- 48,000 BTU: up to 65 m² (medium commercial spaces)
- Over 65 m²: a multi split, ducted system, or professional evaluation is recommended
Factors that increase BTU needs
- A lot of direct sun on the space
- Very high ceilings
- More than two people regularly in the space
- A kitchen or other heat-generating equipment
- Top floor of the building (heat from the roof)
Why it's not worth guessing
An oversized unit turns on and off too often, dehumidifies poorly, and uses more electricity than necessary. An undersized unit never cools properly, runs constantly at full capacity, and wears out faster.
Why the right size matters
An undersized unit runs nonstop on hot afternoons and still cannot reach the temperature you set. It uses more electricity and wears out sooner. An oversized unit is not better either: it cools the air so quickly that it shuts off before it has removed the humidity, leaving the room cold but damp and sticky. It also turns on and off constantly, which shortens the life of the compressor.
Adjustments for Costa Rica
- Region: the table is a good starting point for the Central Valley. In Guanacaste, the Pacific coast or the Caribbean, where it is hotter and more humid, it often makes sense to go one size up.
- Roof: a metal roof without insulation or a top-floor apartment adds a lot of heat from above.
- Windows: large windows facing west receive the strongest afternoon sun. Glass walls can change the calculation completely.
- Use: a home office with computers, a kitchen or a gym needs more capacity than a bedroom of the same size.
A practical example
A 15 m² bedroom in the Central Valley, with a normal ceiling and little direct sun, is well served by a 12,000 BTU unit according to the table. The same bedroom on the top floor with a west-facing window, or in a hot coastal area, may need the next size up. That is why we always look at the actual space before recommending equipment.
For offices, shops and spaces larger than 65 m², a proper heat load calculation is worth it. It considers people, equipment, lighting, insulation and orientation, and it prevents spending money on a system that is either too small or too large.
Before you buy
- Measure the length and width of the room and multiply them to get the area in square meters.
- Note how many hours a day the room gets direct sun and at what time.
- Count the people and the heat-producing equipment that are usually in the space.
- Check whether there is a nearby electrical circuit available for the unit.
Send us these details by WhatsApp with a couple of photos of the space and we can give you an initial recommendation before the visit.
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