Horsepower-hours to British Thermal Units (hp⋅h to BTU)
1 horsepower-hour equals 2,544.433578 British thermal units (rounded).
How to convert horsepower-hours to British thermal units
To convert horsepower-hours to British thermal units, multiply the number of horsepower-hours by 2,544.433578. The factor is rounded to 10 significant digits. To go the other way, multiply British thermal units by 0.0003930147789 (rounded).
British thermal units = horsepower-hours × 2,544.433578
Example: 10 horsepower-hours = 25,444.33578 British thermal units.
The 'calorie' on food labels is really a kilocalorie. The thermochemical calorie (4.184 J) is used here unless marked IT.
About these units
Horsepower-hour (hp⋅h)
About 2.685 MJ (0.7457 kWh), the energy of one mechanical horsepower for an hour.
Multiplying a power by a time gives energy, and this unit does it with James Watt's horse. In the late 18th century Watt compared steam engines with the draft horses they replaced. After an experiment in 1782 that suggested a brewery horse delivered 32,400 foot-pounds per minute, he and Matthew Boulton rounded the figure to 33,000 foot-pounds per minute the next year. One mechanical horsepower is therefore about 745.7 W, and sustaining it for an hour gives roughly 2.685 MJ, or 0.7457 kWh.
The unit is now outdated and outside the SI. Railways still use it to settle accounts when locomotives are lent between companies. In one example, a 2,500 hp unit used for 12 hours is owed back as 30,000 hp-hours, repayable with a 3,000 hp unit for 10. A German variant, the Pferdestaerkenstunde, uses the metric horsepower of about 735.5 W and equals 2,647.7955 kJ, so one hp-hour is about 1.014 PSh.
1 horsepower-hour = 2,684,519.538 joules (approximately).
Sources: Wikipedia: Horsepower-hour; Wikipedia: Horsepower; Wikipedia: Conversion of units of energy
British Thermal Unit (BTU)
The International Table BTU, exactly 1,055.05585262 joules. The energy to heat one pound of water by one degree Fahrenheit; used for heating, cooling and gas appliances in the US.
Few energy units come in as many versions as the British thermal unit. It was defined as the heat needed to raise one pound of liquid water by one degree Fahrenheit, but because water's heat capacity shifts slightly with temperature, definitions differ by up to 0.5 percent: about 1,054.35 J for the thermochemical Btu, 1,054.80 J at 59 degrees Fahrenheit (used for American natural gas pricing), 1,054.68 J at 60 degrees (mainly Canadian), and 1,059.67 J at 39 degrees. A 1942 note suggests the term apparently arose in the United States and was later adopted in Britain.
The version on this site is the International Table Btu, about 1,055.06 J, which comes from the international steam table conferences that tied heat units to the joule. Joule's own 1850 experiments gave 772.692 foot-pounds of work per Btu, the number that first linked heat to mechanical effort.
Today the Btu survives in natural gas pricing (MMBtu means a million Btu), US building energy reporting, and equipment ratings in Btu per hour. One ton of air-conditioning is 12,000 Btu/h, or 3.52 kW. A single wooden kitchen match burning releases about one Btu.
1 British thermal unit = 1,055.055853 joules (approximately).
Sources: Wikipedia: British thermal unit; Wikipedia: James Prescott Joule
Related conversions
- British thermal units to horsepower-hours (reverse)
- Horsepower-hours to joules
- Horsepower-hours to kilojoules
- Horsepower-hours to watt-hours
- Horsepower-hours to kilowatt-hours
- Horsepower-hours to calories
- Horsepower-hours to kilocalories
- Joules to British thermal units
- Kilojoules to British thermal units
- Watt-hours to British thermal units
- Kilowatt-hours to British thermal units
- Calories to British thermal units
- Kilocalories to British thermal units
- Megajoules to British thermal units
- Gigajoules to British thermal units
- Megawatt-hours to British thermal units
- Foot-pounds to British thermal units
- Millijoules to British thermal units
- Electronvolts to British thermal units
See all energy units.