Horsepower to BTU/hr Converter
Convert horsepower (HP) to BTU per hour or BTU/hr to HP instantly.
What the horsepower to BTU/hr converter does
The horsepower to BTU per hour converter changes a power figure between the two units most often mixed in heating, cooling and engine work. Enter a value, choose the direction, and press Calculate. One mechanical horsepower equals 2,544.43 BTU/hr, and the tool multiplies or divides by that factor.
The conversion factors
- 1 hp (mechanical) = 2,544.43 BTU/hr = 745.7 W
- 1 BTU/hr = 0.000393 hp = 0.2931 W
- 1 kW = 1.341 hp = 3,412.1 BTU/hr
The factor comes from the definitions: a horsepower is 550 foot-pounds per second, and a BTU is 778.17 foot-pounds of energy. 550 × 3,600 ÷ 778.17 = 2,544.4.
Worked examples
| Item | Horsepower | BTU/hr | kW |
|---|---|---|---|
| Small pump motor | 0.5 | 1,272 | 0.37 |
| Garage air compressor | 2 | 5,089 | 1.49 |
| Ton of refrigeration (12,000 BTU/hr) | 4.72 | 12,000 | 3.52 |
| Residential furnace output | 31.4 | 80,000 | 23.4 |
| Car engine | 150 | 381,700 | 111.9 |
| Commercial chiller | 393 | 1,000,000 | 293 |
Where the conversion is used
- Compressor and chiller sizing. Refrigeration capacity is quoted in BTU/hr or tons, compressor motors in horsepower. The two are linked by the coefficient of performance: a 5 hp compressor (12,700 BTU/hr of input power) with a COP of 3 delivers about 38,000 BTU/hr of cooling.
- Heat from motors. Every horsepower of motor load in a room ends up as heat. A workshop with 10 hp of running machinery adds 25,400 BTU/hr to the cooling load, about two tons.
- Engine cooling. Roughly a third of an engine’s fuel energy leaves through the radiator. A 150 hp engine at full load rejects on the order of 380,000 BTU/hr of heat, which sets radiator and fan size.
- Boilers and steam. Boiler horsepower is a different unit, 33,475 BTU/hr, and should not be confused with mechanical horsepower.
Different kinds of horsepower
| Unit | Watts | BTU/hr | Used for |
|---|---|---|---|
| Mechanical (imperial) hp | 745.7 | 2,544.4 | Engines, motors in the US and UK; this converter |
| Metric hp (PS, CV) | 735.5 | 2,509.6 | European car engines |
| Electrical hp | 746 | 2,545.5 | Electric motor nameplates |
| Boiler hp | 9,810 | 33,475 | Steam boilers |
The mechanical and electrical values differ by 0.04%, which never matters. Metric horsepower is 1.4% smaller; for a 300 PS engine that is a 4 hp difference.
Input versus output
Motor nameplates give output (shaft) horsepower. The heat a motor adds to a room is its input power, which is output divided by efficiency, plus any work that stays in the room. A 10 hp motor at 90% efficiency draws 11.1 hp of electrical power; if it drives a fan whose air stays in the room, all 11.1 hp (28,300 BTU/hr) becomes heat. If it drives a pump moving water out of the space, only the 1.1 hp of losses (2,800 BTU/hr) heats the room.
Common mistakes
- Using boiler horsepower with the mechanical factor. They differ by a factor of 13.
- Confusing BTU with BTU/hr. BTU is energy; BTU/hr is power. Only power converts to horsepower.
- Forgetting COP for refrigeration. Cooling capacity is several times the compressor’s horsepower equivalent.
- Applying metric PS figures as hp. Multiply PS by 0.986 first.
Related tools
The power converter handles watts, kilowatts and tons of refrigeration. The energy converter covers BTU, joules and kilowatt-hours, the heat flux converter deals with power per unit area, and the horsepower loss calculator estimates engine output at altitude and temperature.
External references
Frequently asked questions
How many BTU/hr is 1 hp?
2,544.43 BTU/hr for mechanical horsepower, or about 2,545 for electrical horsepower.
How many horsepower is a ton of cooling?
A ton is 12,000 BTU/hr, equal to 4.72 hp of heat removal. The compressor driving it typically needs 1 to 1.5 hp of shaft power per ton.
Can I convert BTU (without per hour) to horsepower?
No. BTU is energy. Divide BTU by the number of hours over which it is delivered to get BTU/hr, then convert.
Is the factor exact?
To six significant figures, 1 hp = 2,544.43 BTU/hr using the International Table BTU. Other BTU definitions differ by under 0.1%.
Why do heaters quote BTU/hr but air conditioners quote tons?
Tradition. A ton of refrigeration is the cooling from melting one short ton of ice per day, which works out to 12,000 BTU/hr.