1. Get at least three quotes. There is a good chance you'd want to stay away from the lowest quote, particularly if it is real low compared to every one else.
2. HVAC contractor should do a heat loss heat gain on your home to determine the proper size unit for your home. He can do this at your home or take the information and do his figures that night.
3. HVAC contractor should get back to you no later than the next day.
4. The HVAC contractor should ASK YOU numerous questions pertaining to any past issues or complaints about the previous system, and give you ideas of how any past problems can be solved.
5. The HVAC contractor should at least give you two options, the "good and better" at least, and expain the difference between the two (probably variable and non variable speed, which could also increase the systems performance/ratings.
6. Due to the age of the duct system (assuming it's as old as the last system) the contractor should NOT offer you anything higher than a 15 SEER unit UNLESS he is also quoting you to replace your existing ductwork as well (sit down for that quote). Chances are you have some duct leakages (which the contractor may want to fix).
7. The more detail the quote, the better. Keep in mind, you can have two quotes that could vary by more than 5 grand, and the one for 5 grand more may be worth every penny depending on what needs to be done. The good contractor IMO explains to why his price is what it is. To replace just a heat pump and air handler will cost substantially less than than replacing the heat pump, upgrading the electric, putting in two more supply and return runs and installing a media air cleaner and replacing the lineset (which is recommended when going from R22 to R410A instead of just flushing).
8. Stay away from any HVAC contractor who "bad mouths" another line of equipment that they don't handle. The fact is, most problems with HVAC systems can usually be traced back to sloppy instals. Some guys like to use the cheapest silver solder available (about a $30 difference), however, on an R410A system, that $30 bucks the contractor just saved could cost you a $2,000 bill five years down the road. Another fact is that there is no manufacturer out there that hasn't had some problems or issues in the past. Name the equipment and in the past somewhere there was a tech tip on something the factory has found. Go with a "higher line" per brand name, and you could be paying a pretty penny after the 10 year parts wrty expires for an OEM part. Go with a "builders grade" line, and even an inexperienced person could see what the differences are in the "build quality".
9 The contractor should at least let you know that you can qualify for the federal tax credit by hitting 15 SEER, 8.5 HSPF, 12.5 EER with the system (usually with variable speed, but some lines will do it with an X-13 motor).
10. Contractor should offer you a labor wrty as well IMO, which I highly suggest you consider, as long as you know it's a reputable contractor. Yes, the compressor may have a 10 year warranty, but have it go bad in the eighth year, and you will still be spending a big buck on labor to replace it.
11. Go with the contractor who has made you felt the most comfortable and has explained everything that you have asked questions on. Personally, I rarely go with the highest quote given to me, nor do I go for the lowest quote (sometimes you need to run if it's so low). You want to ensure that the contactor stands behind his work. Don't be afraid to ask for references.
Our Rheem heat pump is on its eleventh year. I sometimes wonder how long to expect it to last. Of course, we've only been here a bit over 4 years and so far, so good.
Example on past issues. Rheem had MAJOR issues due to leaks on their indoor coils some time ago. Such a problem, that some guys swore off Rheem/Ruud (same equipment, different logo). Just a little while ago they had an issue with some X-13 motors in package units. One manufacturer currently has some major reversing valve issues (keep in mind, most of these parts are not made "in house" and are actually made by another company). Two others recently had a bad rash of TXV's. The list can go on and on.
As I tell people, it's not the equipment, but the people who stand behind it
Put it to you this way, there isn't a piece of equipment made today that shouldn't work if installed properly. Keep in mind however, that some equipment is louder than others. This could be a problem if the outdoor unit is right outside your bedroom window.