The middle of winter and summer is when air conditioning systems are most in demand, causing prices to skyrocket. The best time to replace your HVAC system is early spring or early fall. September is a good month to consider replacing your air conditioning system before you start relying on it this winter. Not only that, but you don't want to go a few winter weeks without heating, as installation times are longer due to this additional demand.
The best time to buy an air conditioning system is just when spring or fall begins. The best thing to do is to contact your trusted local HVAC service company. Then, not only will they have more time, but they are likely to have a relationship with several HVAC dealers who can offer you the best deal with the key features that you want.