What If I Undersize My Air Conditioner?

Undersized

• An air conditioner that is undersized in terms of BTUs will not generate sufficient energy to cool the room. An undersized unit will be forced to overwork. This can lead to a room that never reaches the right degree of cooling. The higher the energy use, the higher your energy costs, and the greater the possibility that your unit will malfunction, leading to repair costs.

Oversized

• Selecting a unit that is oversized, or too big, is a common mistake. The thought is that by using a system with more power, there should be no problem in generating the correct amount of cooling. This is not the case. An oversized unit uses more BTUs than necessary, which is a waste of energy and leads to costly repairs and bigger utility bills.

The Right Size

• There are several BTU calculators and worksheets on the Internet. Those on EnergyStar.gov and ConsumerReports.org will help you determine exactly how many BTUs you need -- whether it's for a window box unit or an HVAC central air conditioning system to cool your entire home.