EIA Energy Kids Page

Energy Calculator - Common Units and Conversions
1 cubic foot of natural gas = 1,031 Btu
1 Therm = 100,000 Btu
1 kilowatthour of electricity = 3,412 Btu
1 KW-hour = 0.03412 Therm
1 ton = 12,000 btu/hr
1 btu = 1055.0599 joule

1 cord of firewood = 4'x8'x4'
1 cord of average dry hardwood = 6158 kilo-watt-hour = 210.11 therm
1 cord of wood (between green and air dry red oak) = 19.6 MBtu
1 cord of green hardwood = 5132 (6158/1.2) kWh = 175.07 therm

Propane 91,690 BTUs/gallon
1 tank = 4.73-gallon (20 lb) = 433.6937 kBTUs
1 cynlinder = 0.242 gallon = 22.18 kBTUs

Energy density
Gasoline contains about 42.4 MJ/kg (120 MJ/US gal, 33.3 kWh/US gal) = 113738 btu/gl

For electricity heat to be cheaper than gas,
gas/electricity > 100000/3412 * AFUE(80%) = 23.45

Kerosene vs Electric heater
43.1 MJ/kg / K $/kg = 43.1 / K
3.6 MJ / E $ = 3.6 / E
Kerosene is cheaper if K/E < 12 (kg) or 9.58 (l) or 36.26 (gallon) (density = 0.8)
E = $0.16, K = $5.8/gallon
E = NT$4 台灣電力公司電價表, K = NT$48/kg = NT$38.3/l 台灣中油 煤油