http://www.goodmanmfg.com/consumer/s...dSite=Goodman#

Link to Goodman's 12 SEER unit. Click Product Specs. Scroll down to witness yourself that, depending on coil and furnace used, this so-called 12 SEER ranges from 11 to 13.

If I come across a document regarding the testing for ratings, I will post that as well.