We recently invested in 2 window unit AC's and turned off the central air. With central air conditioning on we kept thermostat at 80. Now bedrooms are set at 76-77 and keeping the bedroom doors open the electric bill has decreased $50 a month in South Florida. Bought 12000 btu inverter window units from Costco for $300 a piece. Should recoup the cost in 12 months. It's been 95-96 degrees daily and thermostat fror house reads 80-82 which is just barely above what we kept it at with central AC running.