Energy efficiency of air conditioning equipment is measured by a standard called Seasonal Energy Efficiency Ratio or SEER rating. This rating is used to compare the electrical efficiency of air conditioning equipment, similar to the way you might compare the efficiency of a car using miles-per-gallon. Technically, the SEER rating is a measure of the total cooling output of the unit over an entire summer in BTUs, divided by the amount of energy it used in Watt-Hours. But what you mostly need to know is that the higher the SEER rating, the more efficiently your air conditioning system provides cooling.
A few years ago, it was pretty normal to have a 10 SEER air conditioner. But as those systems have aged and been replaced, newer air conditioning units have become more efficient. From 2006 to 2014, the federal government mandated that all new air conditioning equipment manufactured in the United States achieved a 13 SEER rating. SEER 13 is approximately 30% more efficient than a SEER 10 air conditioner. This standard remained in place for nearly a decade. Then starting in 2015, the federal government split the SEER requirements into regional areas. Northern climates that use air conditioning less continue with the 13 SEER standard. For Southern states, including South Carolina and North Carolina, the SEER rating minimum increased to SEER 14. The desert states of the Southwest have even stricter energy standards that goes beyond the SEER rating. The 14 SEER minimum now applies to all air conditioning units and heat pump units installed in our Charlotte metro service area.
Higher SEER Ratings
Air conditioning manufacturers have improved their technology steadily since the 2006 mandate, so that now units that meet the 14 SEER standard are the least expensive, lowest model options available. Many Trane air conditioning units are now 16 SEER and above. The highest SEER model Trane manufactures is rated up to 21 SEER, much higher than the technology allowed air conditioners to go just a few years ago.
To achieve higher SEER ratings than 16, most mid-level and higher-end air conditioning units start using two-stage or variable compressor systems. Standard air conditioners are either on or off, but two-stage units allow for low speed cooling on milder days and hi-speed cooling for the hottest days. Two-speed systems run on low about 80% of the time, which allows them to use more energy and run more efficiently.
The highest SEER rated air conditioners now use variable speed systems. Not only doest the compressor change how hard it is working, the outdoor and indoor fans also changes speeds. By using as little energy as possible for modest cooling needs and only ramping up when temperatures get really hot, these systems are able to provide the highest efficiency available in the range of 20-21 SEER.
A Word About SEER Ratings
SEER ratings are obtained by measuring equipment performance in a lab setting without an air duct system. They do not simulate the actual conditions that your equipment will be operating under after installation in your home. Actual system performance varies, based on the quality of the air duct system the equipment is connected to and the quality of the installation procedures used by the installing contractor. In most cases, a new A/C system will save you money on utility bills, but the SEER rating is simply one of the factors for consideration. All systems must be tested with approved testing methods and instruments after installation to insure that potential energy savings of the new equipment is attained.