A clean, no-nonsense calculator for HVAC, heating, and cooling power. Convert between BTU/hr, watts, kilowatts, tons of refrigeration, and horsepower — with the formula explained.
Also equals
Live visualization
Each particle represents a slice of energy flowing from BTU/hr on the left, through the conversion factor, to watts on the right. Drag the slider — more BTU/hr means denser flow.
Fundamentals
BTU to Watts is a power conversion from British Thermal Unit per hour (BTU/hr) to watts (W). One BTU equals 1,055.05585 joules (J), and one hour equals 3,600 seconds, which fixes the exchange rate at 1 BTU/hr = 0.29307107 W. The conversion links the Imperial System to the International System of Units (SI).
A British Thermal Unit (BTU) is the energy needed to raise one pound of water by one degree Fahrenheit. Equipment specs use BTU/hr — the rate at which an AC removes heat or a heater delivers it.
HVAC equipment uses BTU/hr because U.S. industry grew up around the Imperial System. In physics, it measures the same quantity as a watt — power.
A watt (W) is the SI unit of power — one joule (J) per second. Watts appear on every light bulb, appliance, power supply, and electricity bill, which makes it the common language for power draw and heat output.
Kilowatts (kW), megawatts (MW), and milliwatts (mW) are the same unit scaled by 1,000.
BTU/hr and watts both measure a rate of energy, so converting between them is a single multiplication. The fixed exchange rate is 1 BTU/hr = 0.29307107 W.
The formula
The BTU to Watts formula is P(W) = P(BTU/hr) × 0.29307107. The equivalent division form is P(W) = P(BTU/hr) / 3.412141633. P stands for power. The multiplier is fixed by the BTU definition (1,055.05585 joules) divided by 3,600 seconds per hour.
Multiply BTU/hr by 0.29307107 to get watts.
Going the other way, multiply watts by 3.41214163.
Convert a 12,000 BTU/hr one-ton air conditioner to watts:
The same value equals 3.517 kW, 1 ton of refrigeration (RT), and about 4.716 horsepower (hp). Cooling capacity is the quantity here — electrical draw depends on efficiency (SEER/EER) separately.
To convert BTU to watts, multiply the power in BTU/hr by 0.29307107. Three steps complete the conversion:
Take the power in BTU/hr from the equipment spec label, product sheet, or manufacturer page.
Apply the fixed conversion factor. Dividing by 3.412141633 returns the same result.
Use watts (W) for electrical comparison, kilowatts (kW) for larger systems, or tons for HVAC sizing.
Example: a 5,000 BTU/hr window unit converts to 5,000 × 0.29307107 = 1,465.36 W (1.465 kW). A 15,000 BTU/hr unit converts to 4,396.07 W (4.396 kW).
Reference
This conversion table lists power in BTU/hr and the equivalent power in watts (W) and kilowatts (kW) at the fixed ratio 0.29307107. Values cover 1 BTU/hr through 100,000 BTU/hr, matching the range most residential, commercial, and industrial HVAC calculations need.
| Power (BTU/hr) | Power (W) | Power (kW) | Typical use |
|---|---|---|---|
| 1 BTU/hr | 0.293071 W | 0.000293 kW | — |
| 10 BTU/hr | 2.9307 W | 0.002931 kW | — |
| 100 BTU/hr | 29.3071 W | 0.029307 kW | — |
| 500 BTU/hr | 146.54 W | 0.146536 kW | — |
| 1,000 BTU/hr | 293.07 W | 0.293071 kW | Small space heater |
| 2,000 BTU/hr | 586.14 W | 0.586142 kW | — |
| 5,000 BTU/hr | 1,465.36 W | 1.4654 kW | Window AC (small room) |
| 8,000 BTU/hr | 2,344.57 W | 2.3446 kW | Window AC (medium room) |
| 10,000 BTU/hr | 2,930.71 W | 2.9307 kW | Portable AC |
| 12,000 BTU/hr | 3,516.85 W | 3.5169 kW | 1-ton AC unit |
| 15,000 BTU/hr | 4,396.07 W | 4.3961 kW | Mid-size AC |
| 18,000 BTU/hr | 5,275.28 W | 5.2753 kW | 1.5-ton AC unit |
| 24,000 BTU/hr | 7,033.71 W | 7.0337 kW | 2-ton AC unit |
| 36,000 BTU/hr | 10,550.56 W | 10.5506 kW | 3-ton central AC |
| 50,000 BTU/hr | 14,653.55 W | 14.6536 kW | — |
| 60,000 BTU/hr | 17,584.26 W | 17.5843 kW | 5-ton central AC |
| 100,000 BTU/hr | 29,307.11 W | 29.3071 kW | — |
Compare
BTU and watts measure related but distinct quantities. The sections below cover the difference, the 1-to-1 rate that links them, and whether they represent the same thing.
Drag the slider. Both rulers are aligned so the same physical position shows BTU/hr on top and watts on bottom — visual proof that 1 BTU/hr equals 0.29307107 W.
Watts (W) measure power in the International System of Units (SI), and BTU (British Thermal Unit) measures energy in the Imperial System. Three differences separate the two:
Both relate through 1 BTU/hr = 0.29307107 W, which lets one equipment label translate across electric power, kW, MW, hp, and dBm comparisons.
1 watt (W) equals 3.412141633 BTU per hour (BTU/hr). Five common values:
The reverse direction uses P(BTU/hr) = P(W) × 3.412141633.
No, BTU is not the same as watts. BTU measures energy (about 1,055.05585 joules), and watts measure power (1 joule per second). BTU/hr, which is the form seen on equipment labels, measures a rate of energy transfer and maps 1-to-1 with watts at 0.29307107 W per BTU/hr.
In short: BTU is an energy quantity, watts is a power quantity, and BTU/hr is a power quantity that aligns directly with watts.
Application
The most common real-world use of BTU to watts conversion is HVAC sizing. A rough rule of 20 BTU/hr per ft² covers moderate climates, with climate and exposure shifting the factor up or down.
Uses a simple rule of 22 BTU/hr per ft² for a moderate climate. Real sizing also factors ceiling height, insulation, sun exposure, and occupancy.
Questions
Short answers to the things people actually search for.
Related tools
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Thermal power in mechanical hp for motor sizing.
Metric calorie-based HVAC spec conversion.
Commercial HVAC schedules and boiler plate ratings.
Cooling capacity from BTU/hr nameplate to contractor tonnage.