Convert Horsepower-Hours to Therms

Convert Horsepower-Hours (hp·h) to Therms (thm) instantly and accurately.

Conversion Formula

thm = hp·h × 0.02544433578

About Horsepower-Hours

A horsepower-hour (hp·h) is the energy from one mechanical horsepower (745.6999 W) for one hour - exactly 2,684,519.54 J ≈ 2.685 MJ. James Watt coined the horsepower to compare his steam engines with mine horses; billing in hp·h preceded the kilowatt-hour tariff. The metric horsepower (PS = 75 kgf·m/s = 735.499 W) gives a slightly smaller metric-hp·h = 2,647,795 J, used in European and Japanese engine datasheets. Today the hp·h appears in marine engineering logs, mining energy accounting, and vintage industrial equipment. 1 hp·h = 2.6845 MJ = 0.74570 kWh = 641.19 kcal.

About Therms

A therm is the US natural gas billing unit equal to exactly 100,000 BTU = 105,505,585.262 J ≈ 105.5 MJ. One CCF of average US pipeline gas contains ~1.02 therms. The EIA publishes residential gas prices in $/therm; spot prices at Henry Hub are in $/MMBTU (1 MMBTU = 10 therms). US households average 500-700 therms/year for space heating, water heating, and cooking. A 15 kW domestic boiler running 2 hours delivers ~1 therm of useful heat. 1 therm = 100,000 BTU = 105.506 MJ = 29.307 kWh = 25,200 kcal.

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