When your AC breaks down, you need air conditioning unit replacement before the next time the weather turns. Hasty AC replacement can lead to discomfort and high utility bills. Use these four tips to make the most of your AC replacement.  1. Set Your Budget The average cost for AC replacement is $7,870. The cost varies based on the HVAC system you choose and the cost of installation, which varies based on the unit(s) and your current setup.