What Is the BTU System?

Btu

• A Btu represents the amount of heat necessary to raise the temperature of one pound of water by one degree Fahrenheit. In this regard, it is the same concept as a calorie, although the Btu uses the Fahrenheit scale rather than Celsius. To raise the temperature of ten pounds of water by ten degrees requires one hundred Btu's. Because of this, the water would also be said to contain, or hold, 100 Btu's of energy.

Energy

• This energy holding measurement is why the Btu is useful in comparing sources of energy. An amount of coal, oil or gasoline is said to contain a certain amount of energy --- Btus --- that are released upon combustion. Comparing the cost per a set number of Btus is important in determining the efficiency of fuels. A barrel of oil contains 5.6 million Btus while a ton of coal has approximately 25 million Btus.

Home Heating

• In home heating, the output Btu is used to measure how much heat a furnace will produce within a defined period. Heating units are rated on their ability to add heat to an area, the heating capacity of the unit. Getting the proper size unit for the area is important. A unit that is too large will cycle on and off too often, which can damage the unit. A too-small unit will run too much and may not completely heat the home.

Air Conditioning

• For air conditioning, the rating is used to measure how many Btus of heat the unit will remove from an area in a set amount of time. The Btu rating is therefore helpful in deciding how large a unit to use. Larger rooms typically require a higher Btu rating; but like with heaters, too large is inefficient. Likewise, using a unit that is too small is inefficient and will not properly cool the room because the unit can't remove enough Btus from the area.