Energy Conversions

Energy

Note: many energy conversions are approximate because of the varying heat content of fuels, and the temperature and pressure conditions that are assumed.

1 British Thermal Unit (BTU) = the heat required to raise the temperature of 1 pound of water by 1°F

To generate 1 kilowatt-hour (kWh) requires 10,000 Btu of fuel burned by average utility

1 kW = 1000 Watts

1 Btu/hour = .293 Watts

1 Btu = .293 watt-hour

1 kilowatt (kW) = 1.341 horsepower (hp)

1 kilowatt-hour (kWh) = 1.341 horsepower-hour

1 horsepower (hp) = .746 kilowatt (kW)

1 horsepower-hour = .746 kilowatt-hour (kWh)

1 horsepower-hour = 2545 Btu

1 kilowatt-hour (kWh) = 3412 Btu

1 Megawatt = 3,413,000 Btu/hour

1 boiler horsepower (Bhp) = 33,472 Btu/hour output

1 boiler horsepower (Bhp) = 41,840 Btu/hour input @ 80% efficiency

100 boiler horsepower = 42 therm input @ 80% efficiency

1 boiler horsepower (Bhp) = 9803 Watts

1 lb steam/hr (300 psi, saturated) = 1202 Btu/hr

1 therm = 29.3 kWh

1 therm = 100 ft³ natural gas (approximately)

1 therm = 100,000 Btu

1 mmBtu = 1 MBtu = 1 million Btu

1 lb/mmBtu = 1.548 kg/MW-hour

1 ft³ natural gas = 1030 Btu (heat content of gas varies)

1 mmBtu = .9649 thousand cubic feet (Mcf) natural gas

1 lb of fuel oil = 19,000 Btu (approximately)

1 ton of refrigeration = 12,000 Btu/hour

1 ton of refrigeration = 3.516 kW

kWh x .003412 = mmBtu

mcf / .9649 = mmBtu

1 degree-day = the difference between the base temperature for a building and the average outside temperature calculated over the period of one day

base temperature = the outside temperature at which no heating or cooling is needed for a building

Pressure

1 atmosphere = 14.7 pounds per square inch absolute (psia)

1 pound per square inch (psi) = .068 atmosphere

1 atmosphere = 760 mm (29.92 inches) mercury with density of 13.6 grams per cubic centimeter

1 psi = 2.04 inches head of mercury

1 millimeter of mercury = .00132 atmosphere

1 millimeter of mercury = .0193 psi

1 psi = 2.31 feet head of water = 27.7 inches head of water

1 inch head of water = 5.20 pounds per square foot

1 foot head of water = .433 psi

psi = H₂O column in feet x .433

Temperature

°F = (°C x 9/5) + 32

°C = (°F – 32) x 5/9

Kelvin (K) = °C + 273.15  (a version of the celsius scale based on absolute zero)

Rankine (°R) = °F + 459.67  (a version of the fahrenheit scale based on absolute zero)

Volume

1 standard cubic ft is at standard conditions of 60°F and 14.7 psia

1 U.S. barrel = 42 U.S. gallons

1 trillion barrels = 1 x 10¹² barrels

1 KSCF = 1000 standard cubic feet

1 cubic foot water = 7.48 gallons

Weight

1 kilogram (kg) = 1000 grams = 2.205 lbs

1 lb = 7000 grains

1 lb = .454 kilograms = 454 grams

1 ton = 2000 lbs

Miscellaneous

1 year = 365 days

1 year = 8760 hours

Density of water = 8.337 lb/gal

Light bulbs

Lumen output vs watts (note that research continues to improve the watts/lumen for LED’s)