Central air conditioning systems are designed to cool an entire home using refrigeration technology. They consist of a large compressor and coil that are installed outside and connected via refrigerant lines to a coil mounted in your furnace. The duct system is used to distribute hot air in the winter as well as cool air in the summer.
Choosing the right size of air conditioning system for your home requires a close look at different factors that affect your home’s internal temperatures. They include:
- The home’s age
- Total volume of all living spaces
- The number and orientation of your windows
- How much sunshine can enter the home
- Type and condition of existing ventilation system and ductwork
- Is there room above your furnace for the coil? In some homes the furnace may be in a crawlspace or otherwise not have enough room to fit the new central A/C’s coil.
Buying the right size for your home is important. If the system you select is too big, it will over-cool the air and turn off too quickly. The walls, furniture, and other structures will not be sufficiently cooled, however, causing the AC to start up again and create an expensive series of ‘short runs’. Undersized systems are just as problematic, as they will waste energy -and cost money- by running continuously, struggling to adequately cool the home.
Once you source a system that is the right size to cool your home, you will want to check its Seasonal Energy Efficiency Ratio (SEER) rating. The higher the rating, the less energy it will consume. ENERGY STAR® qualified systems range between 12 and 23 SEER.
Note room air conditioners are typically rated using Energy Efficiency Rating (EER), while central A/Cs are typically rated using SEER (source).