What is the most important thing to consider when buying a new air conditioner?

Answer 1

[From Sizing Residential Heating and Air Conditioning Systems at the U.S. Department of Energy Website] When it's time for a new replacement, choosing one of the correct size (heating and/or cooling output) is critical to getting the best efficiency, comfort, and lowest maintenance and operating costs over the life of the new system. The most common sizing mistake is in oversizing. This not only makes the new system cost more to install, but also forces it to operate inefficiently, break down more often, and cost more to operate. Oversized heating equipment also often creates uncomfortable and large temperature swings in the house. Oversized air conditioners (and heat pumps) do not run long enough to dehumidify the air, which results in the "clammy" feeling and unhealthy mold growth in many air-conditioned houses. It is the installer/contractor's job to perform the correct sizing calculation for the building. However, some national surveys have determined that well over half of all HVAC contractors do not size heating and cooling systems correctly.

Answer General rule - Northern Climate (1 ton per 700-1000sf of living area), Southern Climate (1 ton per 400-700 sf of living area). 1 ton = approx. 12000 btu's (if my memory is not failing me) this general calculation should give you enough info. to pick out an adequate AC. Keep in mind that this calc. is a general approximation & does not take into account rooms with excessive window exposure on the sun-side (southern) of the house.

Answer The Energy Efficiency Rating (EER) rating. If it is MORE than 10, do NOT buy it. The lower the number, the better, and the less electricity it uses.

For air conditioning the SEER (seasonal energy efficiency ratio)is used with 10 being considered the MINIMUM for new systems - the higher the better.

Answer 2

Area of space to be cooled, voltage available where the unit will be plugged in, size of window.