BTU to Watts Calculator
Heating and cooling gear is often rated in BTU per hour, while electrical power is in watts. This calculator converts between them.
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How it works
Thermal watts = BTU per hour × 0.293071. Kilowatts = watts ÷ 1000. This is heat-transfer rate, not automatically electrical input. For heating COP, estimated input watts = thermal watts ÷ COP. For cooling EER, input watts = BTU/h ÷ EER because EER is expressed in BTU per watt-hour.
BTU per hour to watts conversion chart
These values convert heat-transfer rate only. “Tons” are nominal cooling-capacity groupings; neither column states how many electrical watts a real unit consumes.
| Heat rate | Thermal watts | Thermal kilowatts | Nominal cooling size |
|---|---|---|---|
| 1,000 BTU/h | 293 W | 0.293 kW | — |
| 5,000 BTU/h | 1,465 W | 1.465 kW | — |
| 9,000 BTU/h | 2,638 W | 2.638 kW | 0.75 ton |
| 12,000 BTU/h | 3,517 W | 3.517 kW | 1 ton |
| 18,000 BTU/h | 5,275 W | 5.275 kW | 1.5 tons |
| 24,000 BTU/h | 7,034 W | 7.034 kW | 2 tons |
| 36,000 BTU/h | 10,551 W | 10.551 kW | 3 tons |
| 48,000 BTU/h | 14,067 W | 14.067 kW | 4 tons |
| 60,000 BTU/h | 17,584 W | 17.584 kW | 5 tons |
The factor uses the International Table Btu. Published equipment values may be rounded, and actual heating or cooling capacity varies with operating conditions.
Worked example: 12,000 BTU/h
Multiply 12,000 BTU/h by 0.293071 to get about 3,517 thermal W, or 3.517 thermal kW. That is a rate of heat moved or delivered—not a statement that the equipment draws 3,517 electrical W.
The conversion follows from the International Table Btu defined by NIST as 1,055.05585262 joules and a watt as one joule per second.
Why a 12,000 BTU/h air conditioner may draw about 1,000 W
Cooling EER is BTU per watt-hour. A 12,000 BTU/h unit operating at EER 12 therefore has an estimated electrical input of 12,000 ÷ 12 = 1,000 W at that rating condition.
Do not divide the 3,517 thermal-watt result by EER; EER already relates BTU/h directly to electrical watts. For a heating COP of 3, by contrast, 3,517 thermal W ÷ 3 gives about 1,172 W of compressor-system input at the stated condition.
BTU and BTU per hour are not the same quantity
A BTU is an amount of energy. BTU per hour is a rate of energy transfer, which is why it can be converted to watts. Heating and cooling equipment labels commonly shorten “BTU per hour” to “BTU,” but the capacity rating normally means BTU/h.
If you have a total amount of BTU rather than a per-hour rate, you also need the time period before converting it to average watts.
Capacity ratings do not replace manufacturer electrical data
Real input changes with efficiency, outdoor and indoor temperature, compressor speed, airflow, defrost, fans, pumps, crankcase heat, and auxiliary electric heat. Use the model’s nameplate and performance tables for operating and electrical requirements.
This thermal conversion is useful for comparing capacity units. It is not suitable by itself for breaker, wire, generator, inverter, or operating-cost sizing.
Sources used for assumptions: NIST — International Table Btu definition and joule conversion; U.S. Energy Information Administration — energy units and Btu conversion factors.
Frequently asked questions
How many watts is 10,000 BTU?
About 2,931 watts (2.93 kW) of heat energy per hour.
Is this the electricity an AC uses?
No — BTU is the cooling/heating output. An efficient AC uses far fewer electrical watts than its BTU rating because it moves heat rather than generating it.
BTU and tons?
12,000 BTU/h equals one ton of cooling, which is about 3.5 kW of heat.
How many electrical watts is a 12,000 BTU air conditioner?
Capacity alone cannot determine input. At EER 12, the rating relationship gives about 1,000 W; the actual model can vary with efficiency and conditions. Check its nameplate and performance data.
Can I convert BTU to watts without hours?
Only if the value is already a rate in BTU per hour. A total energy amount in BTU needs a time period before it can become an average power in watts.
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