Background on Energy Units
calorie – amount of energy needed to heat 1 gram of water 1oC. Used to reflect energy expenditure in ecosystems
Calorie (Kilocalorie) (food Calorie) = 1000 calories
British Thermal Units (BTU) – amount of energy needed to heat 1 lb of water 1oF. Used in home heating/cooling units or appliances that utilize fossil fuels (Gas stove).
Watt – How much potential energy is being used up every second, = 1 joule per 1 second. Used to reflect electrical output.
Horsepower – a unit of power equal to 550 foot-pounds per second (745.7 watts).
Kilowatt-hour (kWh) – amount of energy expended by using 1 Kilowatt of electricity for 1 hour. Used by electrical appliances.
Here are some common conversions. YOU DO NOT NEED TO MEMORIZE THESE. They are usually provided as part of the problem. You do need to be able to apply them.
1 barrel oil = 42 gallons
1 kilowatt-hour = 3.4 x 103 BTU= 8.6 x 105 calories
1 metric ton (tonne) = 1 x 103 kg
1J = W x second or 1W = 1J/second
1kWh = 3.6 x 106 J = 1 megajoules (MJ)
