What is Energy?
Section C. Measuring and Quantifying Energy
1. Conversion and Resource Tables
Energy Conversions
British Thermal Unit Foot-
pounds Joules calories Kilo-
calories Kilowatt-
hours
1 British Thermal Unit 1 777.9 1055 252.0 0.252 2.93x10-4
1 Foot-pound 0.001285 1 1.356 0.3238 3.238x10-4 3.766x10-7
1 joule
9.481x10-4 0.7376 1 0.2388 2.388x10-4 2.778x10-7
1 calorie
0.003969 3.088 4.187 1 0.001 1.163x10-6
1 kilocalorie
3.969 3088 4187 1000 1 0.001163
1 kilowatt hour 3413 2.655x106 3.6x106 8.598x105 859.8 1
Table adapted from "ELEMENTS OF PHYSICS 5/E. by SHORTLEY/WILLIAMS,
1971. Adapted by permission of Prentice-Hall, Inc., Upper Saddle
River, N.J.
For example, this table shows that 1 kilowatt-hour (kWh) = 3413
British Thermal Units (Btu). If you were to convert 15 kWh to Btu,
use the following calculation:
15 kWh x 3413 British Thermal Units = 51,195 Btu
1 kWh
Power Conversions
Foot-Pounds per second Horse-
power calories per second Kilo-
watts Watts
1 foot-pound per second 1 0.001818 0.3238 0.001356 1.356
1 horsepower
550 1 178.1 0.746 746
1 Calorie per second 3.088 0.005615 1 0.004187 4.187
1 kilowatt
737.6 1.341 238.8 1 1000
1 watt
0.7376 0.001341 0.2388 0.001 1
For example, this table shows that 1 watt = 0.001341 horsepower. If
you were to convert 250 watts to horsepower, use the following
calculation:
250 watts x 0.001341 horsepower = 0.34 horsepower
1 watt
Conversion Factors
Average Energy Content of Various Fuels
1 kilowatt hour of electricity = 3413 British thermal units (Btu)
1 cubic foot of natural gas = 1,008 to 1,034 Btu
1 therm of natural gas = 100,000 Btu
Gasoline verses Ethanol BTU's. Check it out.
1 gallon of crude oil = 138,095 Btu
1 barrel of crude oil = 5,800,000 Btu
1 gallon of residual fuel oil = 149,690 Btu
1 gallon of gasoline = 125,000 Btu
1 gallon of ethanol = 84,400 Btu
1 gallon methanol = 62,800 Btu
1 gallon of gasohol
(10% ethanol, 90% gasoline) = 120,900 Btu
1 gallon of E-85
(85% ethanol, 15% gasoline) = 90,500 Btu
1 gallon of kerosene or light distillate oil = 135,000 Btu
1 gallon of middle distillate or diesel fuel oil = 138,690 Btu
1 gallon of liquefied petroleum gas (LPG) = 95,475 Btu
1 pound of coal = 8,100 to 13,000 Btu
1 ton coal = 16,200,000 to 26,000,000 Btu
1 ton wood = 9,000,000 to 17,000,000 Btu
1 standard cord of wood = 18,000,000 to 24,000,000 Btu
1 face cord of wood = 6,000,000 to 8,000,000 Btu
1 pound of low pressure steam (recoverable heat) = 1,000 Btu
