If you are looking to buy a new heating or air conditioning unit, you are likely to have come across the term BTU. This abbreviation is an important factor in choosing the right system for your home. So, it is important to understand the basics.
What is BTU? 
BTU is an abbreviation for the term British Thermal Unit. While the name suggests otherwise, this unit of measurement is no longer used on the market in the United Kingdom. BTU is used as a unit of measurement for energy, and one BTU is calculated as the amount of energy used to increase the temperature for one pound of water by one degree Fahrenheit. While the measurement of BTU has been replaced with the joule, it remains common in heating and cooling appliances or equipment.
How is BTU Used for Heating and Cooling Equipment?
In a furnace or heat pump, the number of BTUs refers to the heating output for the particular unit. The greater the number, the greater the capacity for heat production. The use of BTU is slightly different for air conditioning equipment. The number of BTUs displayed on cooling equipment is used to document how much energy is used to remove heat from the air.
This calculation means that even small air conditioners and heaters can have high BTU figures. Generally, a whole house system will be ranked between 60,000 to 80,000. If you have a smaller home, you are not likely to need a high BTU unit, but larger homes will need the greater capacity of a higher BTU model.
Choosing the Right BTU Appliance:
The BTU of an appliance or unit is a good method of comparing similarly priced systems. Unfortunately, choosing the right BTU is not simply a matter of picking the biggest number. Every property has different heating and cooling needs, so a one size fits all approach is not appropriate. There are a number of factors that will determine the power needed for your home. These factors include the quality and type of insulation in your home, the size and type of windows, the height of your ceilings and the location and exact size of the property.
Since higher BTU units tend to be more costly, choosing too high a capacity can be a waste of money. If you choose a unit or appliance with too low a BTU, it may be underpowered for your requirements. Additionally, since the BTU measures the output capacity for a system, if you are looking to achieve optimum energy efficiency, you will also need to consider the Annual Fuel Utilization Efficiency or AFUE rating of a furnace. A higher AFUE number shown on a furnace indicates that the unit is more efficient and wastes less energy. Heat pumps and air conditioners use the Seasonal Energy Efficiency Ratio or SEER to indicate the cooling process efficiency. This means that to balance efficiency and performance, you need to consider both the BTU and AFUE or SEER. Fortunately, professional HVAC contractors and companies can provide guidance and assistance to determine the correct size of appliance or unit for your home.