Quick Answer: BTU per hour to Watts
One BTU per hour is approximately 0.2931 watts (1 BTU/h ≈ 0.2931 W).
Conversely, 1 W ≈ 3.412 BTU/h.
Formula: W = BTU/h ÷ 3.4121416
Worked examples
- 3412.14 BTU/h ≈ 1,000 W
- 5000 BTU/h ≈ 1,465.36 W
- 9000 BTU/h ≈ 2,637.64 W
Method and limitations
Divide BTU per hour by 3.4121416 to get watts — the unit European HVAC equipment and all electrical calculations use. Calculations use full-precision constants; answers in this box are rounded for readability (≈ marks a rounded value) and the calculator shows up to 9 significant figures. BTU here is the International Table BTU (1,055.05585262 J). BTU/h is power — a rate — not an amount of energy; a heating or cooling rating describes output, not electricity drawn.
Each factor is exact by definition, derived from exact definitions, or a documented conventional value — see the methodology and sources.
Conversion Formula
Divide BTU per hour by 3.4121416 to get watts — the unit European HVAC equipment and all electrical calculations use.
Thermal output is not electrical input
BTU/h and watts are both units of power — energy per unit time — so this is a fixed conversion: 1 BTU/h = 0.29307107 W. Air conditioners and heat pumps are often rated in BTU/h for their heating or cooling output.
That output is not what the unit draws from the socket. For a heat pump or air conditioner, electrical input = thermal output ÷ COP (or EER for cooling) at the stated test conditions. Illustrative example: a 12,000 BTU/h rating is 3,517 W of heat; at a COP of 3 the electrical draw at that operating point would be about 1,172 W. Real COP changes with outdoor and flow temperature, so use the manufacturer's figure for your conditions.
To turn ratings into running cost, use the heat pump savings calculator; the Heat Pumps guide explains COP and SCOP in more detail.
Constants and their sources are listed on the methodology page.
Complete Guide to BTU per hour to Watts Conversion
What is a BTU per hour?
BTU per hour (BTU/h) is the North American measure of thermal power. Air conditioners, furnaces and heat pumps are all catalogued by it, usually abbreviated in marketing to just "BTU".
What is a watt?
The watt (W) is the SI unit of power. In heating and cooling it expresses thermal output — how fast heat is added to or removed from a space.
How the Conversion Works
One Btu(IT) is 1,055.05585262 joules, and one hour is 3,600 seconds, so one BTU/h equals 0.29307107 W. Inverting gives 3.4121416 BTU/h per watt. The conversion applies to thermal power in either direction of heat flow — heating or cooling.
Why This Conversion Matters
Equipment sold in one market is specified in the other market's units constantly. Sizing a mini-split, comparing a European heat pump with a US one, or checking that a portable AC matches a room load all require this single conversion.
Scientific Context
Thermal output is not the same as electrical input for heat pumps and air conditioners, which move heat rather than generate it. A unit with a COP of 4 delivers four watts of heat per watt of electricity, so the BTU/h rating can be several times the power draw.
Step-by-Step Conversion Guide
Follow these steps to convert btu per hour to watts manually:
Start with your value in btu per hour
Example: You want to convert 9000 BTU/h
Apply the conversion formula
Use the formula: W = BTU/h ÷ 3.4121416
Calculate the result
9000 BTU/h = 2,637.64 W
Verify your answer
Use our calculator above to double-check your manual calculation.
Quick Mental Math Tip
Each 1,000 BTU/h is about 293 W, so 12,000 BTU/h ≈ 12 × 293 = 3,516 W (exact: 3,516.85 W).
Common Conversions
| BTU per hour (BTU/h) | Watts (W) | Watts → BTU per hour |
|---|---|---|
| 3412.14 BTU/h | 1,000 | 3412.14 W = 11,642.7 BTU/h |
| 5000 BTU/h | 1,465.36 | 5000 W = 17,060.7 BTU/h |
| 9000 BTU/h | 2,637.64 | 9000 W = 30,709.3 BTU/h |
| 12000 BTU/h | 3,516.85 | 12000 W = 40,945.7 BTU/h |
| 18000 BTU/h | 5,275.28 | 18000 W = 61,418.5 BTU/h |
| 24000 BTU/h | 7,033.71 | 24000 W = 81,891.4 BTU/h |
| 30000 BTU/h | 8,792.13 | 30000 W = 102,364 BTU/h |
| 36000 BTU/h | 10,550.6 | 36000 W = 122,837 BTU/h |
When You'll Need This Conversion
Reading equipment ratings
Express a BTU/h capacity in watts or kW to compare it with equipment rated in kW.
Heat pump selection
Compare North American and European equipment on equal terms.
Server room cooling
IT equipment heat output is in watts; cooling equipment is rated in BTU/h.
HVAC training
Move between imperial and SI thermal power in load calculations.
Pro Tips for Accurate Conversions
One ton = 12,000 BTU/h = 3.517 kW
The three ways the same cooling capacity is written.
Output is not input
For a heat pump or air conditioner, electrical draw ≈ thermal output ÷ COP (heating) or EER (cooling) at the stated test conditions.
Check which rating you are converting
Datasheets can list nominal, minimum and maximum capacity at different temperatures. Convert the one that matches your comparison.
Common Mistakes to Avoid
Reading BTU as energy rather than power
Product listings drop the "per hour" almost universally.
Air conditioner "BTU" ratings always mean BTU/h.
Assuming BTU/h equals electricity used
Heat pumps move more heat than the energy they consume.
Electrical input = thermal output ÷ COP.
Sizing by floor area alone
Insulation, glazing, orientation and occupancy change the load dramatically.
Use a proper heat load calculation, not a rule of thumb, for permanent installations.
History & Background
Cooling capacity is still often given in BTU/h because of the ton of refrigeration: 12,000 BTU/h, the rate of heat removal that melts one short ton (2,000 lb) of ice in 24 hours (2,000 lb × 144 BTU/lb ÷ 24 h).
Global Usage Today
BTU/h is common in North American equipment ratings; equipment sold in many other markets is rated in kW.
Frequently Asked Questions
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Conversion factors on this page are either exact by definition, derived from exact definitions, or conventional values in documented use. Each is listed with its source in our conversion methodology and sources, which cites the BIPM SI Brochure, NIST Special Publication 811 and the relevant IEC or national standards. Results are rounded for display only; calculations use full precision.