With this sort of work let the HVAC guys do the research for you. Call 3 of them get quotes. Then research what they are offering. Pick the one you like. Last time I did this around 2008 it was about 5k-15k I was quoted. I asked all 3 for a small, medium and large systems. For me it was mostly an in place replacement. The ducts were already there. The refrigerant lines were all ready in place. The biggest cost was the unit themselves and some change out of the controllers. The labor was about 1 days worth of work for 4 guys.
You can also gain quite a bit by just fixing drafts and putting in proper insulation. Which can be much cheaper to do. I also had the guys go thru and fix an leaks in the duct system. That way the air was coming out where it should. It is amazing how badly that is installed many times. I also had them put in an attic fan which vented the attic when it got to about 110F. Insulation would have helped more there and I screwed up and put it off. If your house is older than 2000. I say go thru and review the existing insulation and look for drafts first.
It trimmed my bill from about 350 a month to 200. My new house has excellent insulation the house is slightly bigger and the power bill is in the 80-150 range (less because I got solar, but I figured out the actual cost anyway). It has one unit and an air valve to switch between the floors. So the total cost is lower but the one unit will run longer. That savings I am getting is mostly because of better insulation.
You can also gain quite a bit by just fixing drafts and putting in proper insulation. Which can be much cheaper to do. I also had the guys go thru and fix an leaks in the duct system. That way the air was coming out where it should. It is amazing how badly that is installed many times. I also had them put in an attic fan which vented the attic when it got to about 110F. Insulation would have helped more there and I screwed up and put it off. If your house is older than 2000. I say go thru and review the existing insulation and look for drafts first.
It trimmed my bill from about 350 a month to 200. My new house has excellent insulation the house is slightly bigger and the power bill is in the 80-150 range (less because I got solar, but I figured out the actual cost anyway). It has one unit and an air valve to switch between the floors. So the total cost is lower but the one unit will run longer. That savings I am getting is mostly because of better insulation.