Quick Answer: Watts to BTU per hour
One watt is approximately 3.412 BTU per hour (1 W ≈ 3.412 BTU/h).
Conversely, 1 BTU/h ≈ 0.2931 W.
Formula: BTU/h = W × 3.4121416
Worked examples
- 100 W ≈ 341.21 BTU/h
- 500 W ≈ 1,706.07 BTU/h
- 1000 W ≈ 3,412.14 BTU/h
Method and limitations
Multiply watts by 3.4121416 to get BTU per hour, the power unit used in North American heating and cooling equipment ratings. 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
Multiply watts by 3.4121416 to get BTU per hour, the power unit used in North American heating and cooling equipment ratings.
Complete Guide to Watts to BTU per hour Conversion
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.
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".
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 watts to btu per hour manually:
Start with your value in watts
Example: You want to convert 1000 W
Apply the conversion formula
Use the formula: BTU/h = W × 3.4121416
Calculate the result
1000 W = 3,412.14 BTU/h
Verify your answer
Use our calculator above to double-check your manual calculation.
Quick Mental Math Tip
Multiply watts by 3.4121416 to get BTU per hour, the power unit used in North American heating and cooling equipment ratings.
Common Conversions
| Watts (W) | BTU per hour (BTU/h) | BTU per hour → Watts |
|---|---|---|
| 100 W | 341.214 | 100 BTU/h = 29.3071 W |
| 500 W | 1,706.07 | 500 BTU/h = 146.536 W |
| 1000 W | 3,412.14 | 1000 BTU/h = 293.071 W |
| 2000 W | 6,824.28 | 2000 BTU/h = 586.142 W |
| 2500 W | 8,530.35 | 2500 BTU/h = 732.678 W |
| 3500 W | 11,942.5 | 3500 BTU/h = 1,025.75 W |
| 5000 W | 17,060.7 | 5000 BTU/h = 1,465.36 W |
| 7000 W | 23,885 | 7000 BTU/h = 2,051.5 W |
| 10000 W | 34,121.4 | 10000 BTU/h = 2,930.71 W |
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
Related Guides & Articles
View allMetric vs Imperial vs US Customary: How the Systems Differ
"Metric vs Imperial" usually hides three systems: the metric system (today the SI), the British Impe...
The Fascinating History of Temperature Scales
Temperature is something we experience every day, yet the scales we use to measure it have fascinati...
SI Units Explained: Base Units, Derived Units and Prefixes
The International System of Units (SI) is the modern form of the metric system, maintained by the In...
The Complete Guide to Unit Conversion: From Basics to Mastery
Unit conversion is the essential skill that bridges the gap between different measurement systems. W...
Want to learn more about electrical conversions?
Browse all electrical articles →People Also Convert
Related calculators users frequently visit alongside watts to btu per hour.
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.