BTU stands for British Thermal Unit, which is the amount of heat required to raise or lower the temperature of one pound of water one degree Fahrenheit. When it comes to heat pumps or furnaces, the BTU number refers to the heat output of a unit. With air conditioners, the BTU number refers to the amount of energy used to remove heat from the air.
A higher number of BTUs doesn’t necessarily mean it’s better. The power you need for your home can depend on the size of your house, your ductwork and the type of windows and insulation. Typically, whole home units range from 60,000 to 80,000 and above. The larger your home, the higher BTU you will probably want. BTU can also be a good way to compare the capacity of similarly priced units.