I have two central a/c units, one for upstairs, one for down with 3,000 total square feet. About 1,800 down, 1,200 up. Anyway, my current units are AWFUL and with temps that have been 90+ for weeks, they've been running 24/7. They can't keep it below 80 down/83 up in prime daylight. It's cooler at night so we are not miserable. A friend in the business diagnosed my compressors as being near deathbed, so I am replacing those this week. I hope it helps because I just got my first utility bill of the summer...cycle closed on JUNE 8th, mind you, not August 8th...and it was $441. I want to die because we've all sweated inside for the last month!! That is the highest I have ever had this early in 8 years! I may have had one other bill over $400 one time when we had a 100+ degreee heat wave. Buying new units and paying my current bill is severely breaking my summer budget!