The Number on the Box Is a Rate, Not a Draw
The most useful thing this conversion does is also the easiest to misread. When a box says 12,000 BTU, it is promising to remove 12,000 British thermal units of heat every hour — that is 3,516.85 watts of cooling, a thermal power. It is not promising to consume 3,516.85 watts. The electrical draw sits on a different label, printed in amps or watts, and for a modern unit it is usually a third of the BTU/h figure or less. The gap between the two numbers is the machine's coefficient of performance, and it is the reason an air conditioner can move three watts of heat for every watt it burns.
watts = BTU/h × 0.2930710702
1 BTU/h = 0.2930710702 W
The factor is exact: 1,055.05585262 J (one IT BTU) ÷ 3,600 s (one hour).
Common Air Conditioner Sizes in Watts
| AC rating | thermal power | typical electrical draw |
|---|---|---|
| 5,000 BTU/h | 1,465 W | ~500–600 W |
| 8,000 BTU/h | 2,345 W | ~750–900 W |
| 12,000 BTU/h | 3,517 W | ~1,000–1,500 W |
| 18,000 BTU/h | 5,275 W | ~1,800–2,200 W |
| 24,000 BTU/h | 7,034 W | ~2,400–3,000 W |
The split between the two columns is where most "how many watts is my AC" searches go wrong. The thermal column is a fixed constant times the rating; the electrical column varies with the machine's efficiency (SEER/EER), the outdoor temperature, and the age of the compressor. No converter can tell you the second column from the first — you need the nameplate's amp rating and the supply voltage, which is where watts to amps picks up the job.
Engineering Context
The same cooling rate in kilowatts is BTU/h to kW, and in the HVAC industry's own trade unit it is BTU/h to ton (with the reverse at ton to BTU/h). For the energy dimension rather than the power dimension — how much heat total, not how fast — the bridge is BTU to kWh and BTU to joules. When the electrical draw itself is the question, watts to kW sizes the circuit and watts to amps sizes the breaker.
More: BTU/h to kW · BTU/h to ton · BTU to kWh · Energy Hub
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Frequently Asked Questions
How many watts is a 12,000 BTU air conditioner?
Thermally, 12,000 BTU/h equals 3,516.85 watts of cooling — that is the heat it removes per second. Electrically, it draws far less, usually 1,000 to 1,500 watts, because an air conditioner is a heat pump: it moves heat rather than creating it, and its coefficient of performance (COP) is roughly 2.5 to 3.5. Never read the BTU-to-watts number off a nameplate as the electrical load.
Is BTU/h the same as watts?
They measure the same thing — power, or energy per unit time — in different units. One BTU/h is exactly 0.2930710702 watts. The difference is only convention: North American HVAC uses BTU/h, the SI world uses watts, and 3,412.141633 BTU/h make one kilowatt. The conversion is a fixed constant, not a measurement.
Why does my 12,000 BTU AC not draw 3,516 watts?
Because 3,516 watts is the rate of heat the unit removes, not the electricity it consumes. An air conditioner transfers heat from indoors to outdoors using a compressor and refrigerant; it takes roughly one watt of electricity to move three watts of heat. That ratio is the coefficient of performance. The electrical draw lives on a separate label, in amps or watts, and is always a third of the BTU/h figure or less.
More: btu/h to kw · btu/h to ton · btu to kwh · Energy Hub