How to Figure BTUs for an HVAC

Right Size

• Bigger is not always better when it comes to HVAC units, according to the U.S. Department of Energy. Units that are too small will have to run too long to try to maintain a comfortable living environment, which results in increased energy usage and costs. Units that are too large will run inefficiently, which will also result in wasted energy. Oversized cooling units tend to cool the air too quickly while failing to remove excess humidity, making the living environment feel clammy, damp and uncomfortable. A properly sized HVAC unit will provide the most comfortable living space with the most efficient use of energy.

BTU vs Ton

• There are two primary measurement units used describe cooling capacity for HVAC units in the United States. The older, outdated method refers to the cooling capacity of HVAC units in tons. A ton of cooling capacity is equivalent to the cooling that results from melting one ton of ice during a 24-hour period. The newer method refers to cooling capacity in British Thermal Units, or BTUs. A BTU refers to the amount of energy required to increase the temperature of 1 pound of water by one degree Fahrenheit. A ton is approximately equivalent to 12,000 BTUs.

Square Footage

• The primary method of determining the proper size for your HVAC unit is by measuring the square footage of the living space that you wish to heat and cool. You will need a 5,000 BTU unit to properly cool an area of up to 150 square feet, according to the U.S. Department of Energy. You will need a 10,000 BTU to effectively cool an area of 450 square feet. An 18,000 BTU unit can handle a home with 1,000 square feet of living space. If your home has 2,000 square feet of space, you will need an HVAC unit of at least 34,000 BTUs.

Considerations

• There are a number of factors other than square footage that can affect the size of your HVAC unit. You can reduce the number of BTUs required to cool your home if the living area is heavily shaded, according to the U.S. Department of Energy. Living spaces that are exposed to full sun may require up to 10 percent additional cooling capacity. If more than two people live in the home, you will need to increase the number of BTUs by 600 for each additional person.