Buying an air conditioner 2026: how many BTU + saving power
Air-con is usually a home's biggest power user, so picking the right BTU for the room and an efficient unit really matters.
Choose BTU by room size
ภาพ: Infrogmation of New Orleans — CC BY-SA (wikimedia)
BTU is cooling capacity — too little and the room won't cool; too much wastes power and cycles often.
| Room size (sqm) | Suggested BTU |
|---|---|
| 15–20 | 9,000–12,000 |
| 21–25 | 12,000–15,000 |
| 30–40 | 18,000–21,000 |
| 40–50 | 24,000 |
If the room gets strong sun, sits under the roof, or holds many people/heat sources, add ~10–20% BTU.
Inverter vs fixed-speed
| Topic | Inverter | Fixed-speed |
|---|---|---|
| Long-term bill | Lower | Higher |
| Unit price | Slightly higher | Cheaper |
| Temperature | Steadier | More swing |
| Best for | Long continuous use | Occasional short use |
Check the efficiency label
Choose a high energy rating and look at SEER — higher is more efficient. Running cost ≈ watts × hours ÷ 1,000 × price per unit.
Verdict
Photo: Shixart1985 — CC BY (wikimedia)
Start by matching BTU to the room, choose an efficient inverter if you run it often, then clean it regularly to keep efficiency and save power. The air-con and the water heater are a home's two biggest power draws, so it's worth choosing both wisely.
Sources
Photo: Dinkun Chen — CC BY-SA (wikimedia)
- Manufacturer manuals/specs
- Energy-efficiency labels and electricity tariff
Frequently asked questions
- How many BTU for a typical bedroom?
- A 15–20 sqm bedroom usually needs around 9,000–12,000 BTU; add a little more if the room gets a lot of sun or sits under a hot roof.
- Are inverter units really more efficient?
- Yes for long continuous use — they vary compressor speed instead of cycling on/off, so long-term bills are lower despite a slightly higher price.
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