Rating of Boiler

Boiler horsepower (BHP) is an obsolete non-metric measurement unit of power. Nevertheless, BHP is still used to measure boiler output in industrial boiler engineering in North America. One Boiler Horsepower (1BHP) is equal to a boiler thermal output of 33,475 BTU/h (British Thermal Units per Hour) or 9.81055407 kW (Kilowatts). This is the energy rate required to evaporate 34.5 lb (pounds) or 15.648936765 kg (kilograms) of fresh water at 212 °F (degrees Fahrenheit) or 100 °C (Celsius) in one hour (1h).

Large boiler capacity is generally given in lbs of steam evaporated per hour, under specified steam conditions. Maximum continuous rating is the hourly evaporation that can be maintained for 24 hours.

To convert horsepower (hp) into lbs of steam: Multiply hp x 34.5

Example: 100 hp x 34.5 = 3450 lbs of steam per hour


To convert lbs of steam to hp: Divide steam per hour by 34.5


Example: 8625 lbs of steam ÷ 34.5 = 250 hp boiler