In case you missed it, there are now new minimum efficiency standards for residential air conditioning equipment. As of January 1, 2015 the long discussed regional air conditioning standards went into effect. They are called regional standards because the minimum legal efficiency of the equipment is determined by the region of the country in which it will be installed. For Northern states, nothing changes – the minimum stays at 13 SEER. For the southeast, the minimum is increased to 14 SEER. For the southwest, the minimum is a bit more complicated. The SEER rises to 14, but minimum EERs are also introduced. The minimum EER for the Southwest is 12.2 for systems less than 45,000 Btuh and 11.7 for systems 45,000 Btuh and greater. So a 13 SEER system that is legal in Indiana is illegal in Kentucky. A 14 SEER system that is legal in Texas might not be in Arizona, depending on its EER. Although the minimum efficiencies are already in effect, the enforcement mechanism has yet to be determined.
It is interesting to note that it is possible for a unit to have a higher SEER than another unit, but for the lower SEER unit to have a higher EER. That is the reason for the dual SEER/EER conditions.
Rheem has a good page with a map and a table explaining the new standards
There is a very informative presentation on the California Energy Commision’s web site by Steve Kavanaugh explaining the reasoning behind using both SEER and EER for minimum efficiency standards.