Central Air Conditioning Cooling Capacity

Tons and BTUs

• The size of your central air conditioning unit has nothing to do with its physical size. Size, in HVAC speak, refers to how many British Thermal Units (BTUs) the system produces per hour. Air conditioners are also referred to in “tons.” For every 12,000 BTUs that are produced per hour an air conditioner is said to be one ton. That is equal to the amount of energy needed to melt one ton of ice in a day.

Importance

• Choosing the correct size air conditioner and its correlating capacity is very important for a few reasons. An air conditioner that is too small for the space it is trying to cool will struggle to keep up and often freezes on the hottest days. On the other hand, a system that is too large cycles on and off too often and does not remove enough humidity from the air inside the home. Improper cooling capacity for your home will result in inefficiency, wasted energy and higher power bills.

Age and Insulation

• The age and insulation of your home contributes to its cooling capacity needs. An older house that is not built as airtight as newer homes will require more BTUs for proper cooling. The amount of insulation in a home also contributes to cooling needs. Lighter insulation means more cooling capacity is required, while better insulation will reduce the needed capacity of the unit.

Windows

• Windows are an important factor in determining cooling capacity needs for your central unit. First, windows let radiant heat into the home in the form of sunlight. This can increase the need from your unit. Older windows may also allow air to leak around the edges, letting cold air out and warm air in. The more windows a home has, the more powerful the air conditioner will need to be.

Square Feet

• As a general rule you can assume a 1,500-square-foot home will need approximately 2.5 tons of central air conditioning to adequately cool the home. Poor insulation, lots of windows, lack of tree shade and the climate in general can cause this figure to be adjusted. Every house has different cooling needs.