Choosing the Right AC Size for Your Room in Thailand
April 10, 2026
An undersized AC will struggle to cool your room. An oversized one wastes electricity and creates humidity problems. Here is how to get it right.
Getting the BTU rating right is one of the most important decisions when buying an AC unit. Too small and the unit runs constantly without reaching your target temperature. Too large and it cools too quickly, shuts off before removing enough humidity, and leaves the room feeling clammy.
The basic calculation for Thailand is: room area in square metres multiplied by 600 BTU. So a 20 sqm bedroom needs around 12,000 BTU, which is a standard 1 ton unit.
But you need to adjust for several factors. If the room gets direct afternoon sun through west or south-facing windows, add 20%. If your ceiling is higher than 2.8 metres, add another 10%. Rooms above the top floor with a roof directly above should add 15% for heat gain.
Kitchen and dining areas generate more heat from cooking and people, so add 10 to 20% for those spaces.
For office spaces, also account for heat from computers, monitors, and people. Each person adds roughly 500 BTU of heat load.
If you are unsure, our team can visit and calculate the exact requirement for each room before you buy. Getting this right means lower electricity bills and a more comfortable space for years to come.
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