How to Choose the Right AC Size for Your Thai Home

Installing an AC that's too small means it runs constantly and never cools properly. Too large, and it short-cycles — cooling quickly but not removing humidity, leaving the room feeling cold and damp. Getting the size right is critical, especially in Thailand's humid climate.

The Basic Formula

Start with: Room area (m²) × 600 = BTU required. For example: A 20m² bedroom needs approximately 12,000 BTU (a standard 1.5-ton unit).

Thailand Adjustment Factors

Add to your base calculation: Direct sunlight on south or west-facing windows adds 20%. High ceilings above 2.8m add 10%. Kitchens or rooms with heat-generating appliances add 25%. Coastal locations add 5% as salt corrosion reduces efficiency faster. For open-plan spaces, calculate total area rather than individual rooms.

Quick Reference Guide

Up to 15m²: 9,000 BTU (1 ton). 15–20m²: 12,000 BTU (1.5 ton). 20–30m²: 18,000 BTU (2 ton). 30–45m²: 24,000 BTU (2.5 ton). 45–60m²: 30,000 BTU (3 ton). Above 60m²: Consider multi-zone or cassette systems.

Inverter vs Non-Inverter

In Thailand, where ACs run 8–16 hours daily, inverter technology is always worth the higher upfront cost. Inverter ACs adjust their power output to match demand — using 30–50% less electricity than fixed-speed models. The payback period is typically 18–24 months.