The energy ratings of air conditioners are based on how many Btu’s (heat) per hour the unit can remove for each watt hour of power it draws.
For central air conditioners, the efficiency rating is called the Seasonal Energy Efficiency Ratio, or SEER.
The most efficient air conditioners are listed by size and efficiency in the Consumer Guide to Home Energy Savings, published by the American Council for an Energy-Efficient Economy.
National appliance minimum standards for central air conditioners require a SEER between 8.9 and 10.0, depending on when the unit was manufactured.
To determine the approximate SEER of an existing CAC find the model number and the manufacturer from the nameplate on the outdoor unit and contact a local dealer and ask them to look it up for you.
Sizing is a very important consideration to achieve comfort and minimize energy cost when selecting new a/c equipment.
The cooling comfort is provided by reducing air temperature and removing humidity. An A/C that runs all the time isn’t necessarily sized correctly. It could be oversized, and straining to overcome maintenance, repair or adjustment problems. Or it could be undersized.
The preceeding is not meant to undermine the intelligence of others but rather to assist those who may not have known as much. Oh well!