I have a 21 year old Rheem Central AC No heat which was installed in 1989 Unit for the most part has been problem free other then 1 or 2 run capacitors and 2 hard start kits never a freon leak original freon. I was thinking about replacing it but my question is how long am i looking at to maybe break even. I am on Long Island and have to pay LIPA's Electric rates are very high. I know it would be cheaper for me to replace it now or during the winter because AC guys are slow now but how inefficent is my system really? What do you guys think of rheem i am thinking if i do replace i should go with another rheem since i have been so lucky? What seer rating do you recommond?