How Many Square Feet Will
An A/C Unit Cool?

When your home was built, your general contractor used many subcontractors who were responsible for the many facets of home building. Cementers, Framers, Electricians, Plumbers, Mechanical Engineers, etc. The mechanical engineer, using a set of plans did what is called a load calculation on the home. The load calculation is the first step for the design and installation of heating and cooling Systems. The Mech. engineers main source of data for calculating both heat and heat gain in residential structures is a book called MANUAL J. It was developed jointly and adopted by the Air Conditioning Contractors of America and the Air Conditioning and Refrigeration Institute.

The calculation procedures contained in MANUAL J is the result of many industry studies of residential heat gains and calculation methods. The manual has some 126 pages, illustrations, figures, tables, and procedures one should use to determine the correct size of unit needed.

Just a few of the factors used to determine unit size is:

Type of floor
Type of wall and it's thickness
Type of wall insulation
Window types
Location of building on property
Ceiling insulation
Window shading
And many, many more factors, one of which is square footage.
So the most important question I might suggest you ask yourself to insure piece of mind is "HOW OLD IS MY OLD UNIT?". The average life span for an A/C or heat pump system is between 8 to 12 years. If your unit is close to that age or older, the chances that your unit may be undersized is very unlikely. An undersized unit would never last that long in.

If your home has been added on to or you require special temperatures, that may be a reason, but bigger is not always better when it comes to air conditioning.