UNITS OF MEASURE:

In our foot-pound system, the unit of heat energy is the British Thermal Unit, or BTU.  That is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.  If you light a paper match, it will put out about one BTU of heat energy before it burns your fingers.

In the Metric (International) system, the unit of heat energy is the calorie, which stands for the amount of energy required to raise one gram of water
by one degree Celsius.

One BTU is equivalent to 252 calories.

For cost per BTU of the fossil fuels, see Cost of Fuels.

Watts measure the amount of electricity needed to run something, as in 100-watt light bulb. One kilowatt means 1,000 watts, and KWH stands for one hour of operation at one kilowatt.

One kilowatt of energy going through an electric heater for an hour will put out 3,713 BTUs of heat in one kilowatt hour (KWH).

Power companies meter electrical usage in KWH.  Recently, the light bill for our home in Plymouth, MA showed that we used 298 KWH in that month. The bill was for $59.60.  Dividing 5,960 cents by 298 showed that we were paying about 15 cents per kilowatt-hour.

When gas is piped into the house by a public utility, the bill is presented in CCF, which stands for hundred cubic feet. However, the bill is probably calculated in Therms, standing for 100,000 BTUs. That’s almost the same thing as CCF, because one hundred cubic feet of this gas contains about 102,000 BTUs.

Packaged Air Conditioners are usually rated according to the BTUs (8500, etc) that they will remove in one hour.  A rating of 13,500 is equivalent to “one ton” of capacity.  That archaic terminology is used on the larger whole-house systems.  It is left over from the days when an AC system that seemed to cool as well as 2,000 pounds of ice was said to have a ton of capacity.

If you think of other energy-related Units of Measure that should be covered here, please let us know.