The Trane XE 1200 air conditioner carries a Seasonal Energy Efficiency Ratio of 12, which means that it is average in terms of efficiency. Federal regulations enacted in 2006 mandate a minimum SEER rating of 13.
Modern air-conditioner models can reach a SEER level of as high as 23, meaning that over the course of their operating life, they cost about half as much to use as a Trane XE 1200. Deciding what SEER level to choose is a function of climate. In warm areas where air conditioning is required year round, higher efficiency equals reduced energy consumption and operating costs.