2. Select Air Conditioner Efficiency Ratings

Air conditioner efficiency is rated in SEER2 (Seasonal Energy Efficiency Ratio). An air conditioner’s SEER2 rating is arrived at by dividing the total cooling output from a piece of equipment in BTUs by the energy it consumes in watt-hours. Most central air conditioners today have a SEER2 rating between 13 and 20, with those at the higher end of this range considered very energy efficient.
It’s important to note, however, that the efficiency of a system and its SEER2 rating depends on all the components in the system and not just the condenser. The SEER2 rating for a condenser is primarily used for marketing and product differentiation and you should always use the rating for a complete matched system when comparing options.
Consider the Local Climate
In climates that are both hot and humid, the higher the SEER will need to be since the air conditioner will be running more often to cool and dehumidify the air.