To reduce wasted energy, the U.S. Department of Energy has established minimum efficiency standards for air conditioners. Every unit is given an efficiency rating, called a SEER (Seasonal Energy Efficiency Rating). This is listed on the yellow Energy Guide label posted on each unit. It’s important to look at these ratings since the higher the number the more efficient the unit and the less it will cost to provide cooling.
The minimum allowable SEER rating for new central air conditioners had been 10, but it was changed to 13 in January 2006. The most efficient models have SEERs of 15–17.
When shopping, pay attention to the terminology. “High-efficiency” models were those rated a 10. “Super-high- efficiency” models had a SEER of 11–12. “Ultra-high- efficiency” models were 12 and over.
To achieve particularly high SEERs, air conditioners may have any number of energy-saving features, typically large coils for more efficient heat transfer and variable-speed blower and fan motors to reduce electricity consumption.
The York Stellar Ultra features two compressors that work in tandem when high cooling capacity is needed; the rest of the time, only one of the compressors operates. These, combined with a variable-speed motor, achieve a SEER rating of 16.7.
Programmable thermostats also help by offering precise control. Another energy-saving feature is a fan that stays on long enough to utilize residual cool air that remains after the compressor turns off. And some units have an indicator light that lets you know when the filter needs changing, which also boosts efficiency by ensuring proper maintenance.
Do you need an ultra-high-efficiency air conditioner? Not necessarily. Of course, for the sake of the environment—from energy usage to greenhouse-gas emissions—the higher the efficiency the better. But, in terms of dollars, the savings compared to the premium you will pay may not pencil out for you, particularly if you live in a climate that requires little cooling during the year or if your home isn't tightly insulated. On the other hand, where an air conditioner must run frequently during the year, a highly efficient model will pay for itself in energy savings over a period of years.
One note about replacing an aging system: Be sure to replace both the outdoor condensing unit and the indoor evaporator. If you just replace the condensing unit, potential gains of a higher-efficiency unit may be lost.
