S.E.E.R. - Stands for Seasonal Energy Efficiency Ratio. Manufactures are required by law to evaluate and rate their air conditioning equipment according to its energy efficiency. They then must submit it to (AHRI) Air Conditioning Heating, and Refrigeration Institute who uses an independent third party laboratory to certify the manufacturer’s claims of efficiency are accurate. The higher the rating or SEER number the less electricity the unit uses. Or the higher the SEER rating the more energy efficient the unit is. The minimum the federal government (talking central air conditioning not portable units), allows manufactures to make in 2011 is a 13 SEER units. Ratings on air conditioning units non-geothermal or without solar panels can reach up to 21 SEER.
The higher the SEER rating, the more expensive the unit. You are paying for the technology, research and development. You invest more up front by installing a high SEER air conditioning system, but will have a return with lower electric bills if you plan to stay in the home. Even people with rental property sometimes feel it reduces tenant turn over by helping to keep electric cost down. Some realtors use newer high SEER equipment as a property selling feature.
You might have wondered if a manufacturer has ever made a claim of efficiency and had it disproved by AHRI. Yes, that has happened. I don’t think it was a matter of dishonesty. But more a matter of a certain condenser being matched with a particular size or type of evaporator coil under worst case scenario they could not attain best case results. Sometimes a higher SEER rating can be attained in a 2 ton unit than a 5 ton (same model), due to larger refrigerant lines, motors and other heavier duty parts that are necessary.
However, this testing and rating is done with a matched system using both a new indoor and new outdoor unit. If you are not replacing your evaporator coil at the same time or mismatching your system with a new outdoor unit to an existing indoor unit; all bets are off. Who knows what efficiency rating you are getting. Units/systems do begin to become less efficient as they age due to wear, cleanliness and rust. So don’t think you can have an eight year old indoor evaporator coil, go buy a new 16 SEER outdoor condenser and get 16 SEER savings on your utility bills. Not going to happen. Will it be better than your old one? Yes. Your old unit was probably rated a 10 SEER when installed eight years ago.