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)
Incandescent | Compact Fluorescent | LED | Lumens |
Watts | Watts | Watts | |
40 | 9-13 | 4-5 | 450 |
60 | 13-15 | 6-8 | 800 |
75 | 18-25 | 9-13 | 1,100 |
100 | 23-30 | 16-20 | 1,600 |
150 | 30-55 | 25-28 | 2,600 |
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