All utilities should be on and system in working condition, if possible. An HVAC tech can check out the units to insure everything is functional and parts are in good condition. A Home Energy Rater should be contacted to do a Blower door test for building tightness and a Duct Blast test to find out how bad the AC system leaks. Since you AC system accounts for up to 50% of your electric bill it is important to fix all of the possible areas that the AIR can escape through.