The first 20 SEER (Seasonal Energy Efficiency Rating)

What is claimed to be the first 20 SEER (Seasonal Energy Efficiency Rating) residential air conditioner has been introduced by Lennox Industries, USA. The XC21 air conditioner has a two-stage scroll compressor and operates on two levels: a high level for cooler weather and a low level that will be operable 80% of the time. It uses R-410A and has a low sound level.