How Much Does Air-Con Cost to Run Work Out the Cost Per Hour
Run the AC all night and worried the bill will spike? This page shows how to calculate AC electricity cost simply — from BTU to watts to units (kWh) to baht — with a cost table for every popular size, the difference between inverter and non-inverter, and practical ways to cut your AC bill at home.
AC cost per hour = the unit's power (kilowatts) × hours × the electricity rate per unit. Example: a 12,000 BTU non-inverter draws about 1,200 watts = 1.2 kW. Run flat-out for 1 hour = 1.2 units × ~4 THB ≈ 4.8 THB/hour; all night for 8 hours ≈ 38 THB (in practice the compressor cycles on/off, so it's usually less). An inverter draws less once the room is cool (often 40-60% of rated power), so it's cheaper over long runs. The real per-unit rate changes each period — see the latest at how many baht per unit 2026.
How to Calculate AC Cost, Step by Step
The key is converting the AC's size (BTU) into power (watts), then multiplying by hours and the per-unit rate. Follow these 4 steps:
1) Find the power in watts — check the AC's label (side plate/manual) for “watts” or “W”. If absent, estimate roughly from BTU: a non-inverter ≈ BTU × 0.1 (a 12,000 BTU ≈ 1,200 W) — but the real nameplate is more accurate.
2) Convert to kilowatts (kW) — divide watts by 1,000, e.g. 1,200 W = 1.2 kW.
3) Multiply by hours = units (kWh) — kW × hours run, e.g. 1.2 kW × 8 h = 9.6 units (kWh).
4) Multiply by the per-unit rate = baht — units × rate, e.g. 9.6 units × ~4 THB ≈ 38 THB/night. Note: this assumes “full power the whole time”; in reality the compressor cycles, so it's usually less — especially for inverters.
The ~4 THB/unit is a round figure for easy math. Real home bills are tiered (more usage = higher per-unit) and include Ft + VAT. See the real tiered rates at how many baht per unit 2026, or compute the full bill at how to calculate your bill 2026.
AC Cost Table by Size (BTU)
Rough cost for a non-inverter at full power, using ~4 THB/unit (an inverter on long runs is often 20-40% cheaper):
| AC size | Power ~ | Cost/hour | Cost / 8 h |
|---|---|---|---|
| 9,000 BTU | ~900 W | ~3.6 THB | ~29 THB |
| 12,000 BTU | ~1,200 W | ~4.8 THB | ~38 THB |
| 18,000 BTU | ~1,800 W | ~7.2 THB | ~58 THB |
| 24,000 BTU | ~2,400 W | ~9.6 THB | ~77 THB |
* Figures are approximations for comparison only. Actual cost depends on the real nameplate watts, the temperature you set, room conditions, the compressor's on/off cycling, and your home's tiered rate. An inverter running continuously usually uses less than this table.
Inverter vs Non-Inverter: How Different Is the Cost?
The main difference is how the compressor works:
Non-inverter (fixed speed)
The compressor runs at full power then cuts off at the target temperature, restarting when it warms up — drawing power in on-off bursts. Cheaper to buy, but usually uses more over long runs. Best for rooms where the AC runs only briefly.
Inverter
Continuously varies the compressor speed to hold the temperature, without hard on-off cycling. Once the room is cool it drops to about 40-60% power, so it's cheaper over long runs (e.g. all night). Costs more upfront but pays off with heavy daily use.
Bottom line: if you only run the AC 1-2 hours a day, a non-inverter is fine; but if you run it all night every day, an inverter usually saves more over time despite the higher upfront price.
7 Tips That Really Cut Your AC Bill
Things you can do at home to cut AC cost without suffering the heat:
Set 25-26°C — every degree lower raises consumption by ~5-10%. Setting 26°C with a fan feels cool enough and is far cheaper than 22°C.
Run a fan with the AC — a fan spreads the cool air so you can set a higher temperature and still feel cool. A fan only uses a few dozen watts.
Clean the AC/filter regularly — a clogged filter makes the unit work harder and use more power. Clean the filter every 1-2 months and do a full service 1-2 times a year.
Close doors/windows to stop heat leaking in — seal gaps where hot air enters and use curtains against sun to reduce the AC's load.
Use Eco/Sleep mode and a timer — use Eco/Sleep mode and an auto-off timer for the late hours when it cools naturally, instead of full power all night.
Match the BTU size to the room — too small and it runs hard non-stop; too big wastes power. Pick the right BTU for the room (roughly 9,000-12,000 BTU for a small bedroom).
Heavy daytime AC? Look at TOU rates — if you use the AC a lot during the day (the expensive On-Peak window), shifting some loads to off-peak or considering a daytime power source can help. See the TOU rate schedule.
About this page
Compiled by the CapSolar team, led by Frank Lee (Founder). The method uses the principle of power (watts) × time × per-unit rate. The table figures are approximations for comparison; actual cost depends on the nameplate, your usage habits, and your home's tiered rate. See the latest per-unit rate on the per-unit page.
FAQ
Heavy daytime AC running up your bill?
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