They've also said that a system is working well even when its 20 degrees behind (set at 72, but 85 inside and 95 outside). I know you may need greater detail, but does anybody have any recommendations short of what my HVAC co recommends (replacement)?

The house is a 2 story house, you're setting the upstairs unit high 85 inside then wanting it to drop to 72?

So are you doing this with the down stairs unit as well?

Remember heat rises, so that upstairs unit is under a much heavier load than the newer downstairs unit. (cooling falls, heat rises)

The spaces are zoned... but there is a tandem going on because both these zones make up the structure. So if the upstairs is a 85 in the heat of the day 3-6pm in some cases 3-7pm / maybe 3-8pm under dire circumstances. It's going to take time depending on more than just a few variables.

It could easily take 4-5 hours to pull down to desired temp... even more so if the downstairs unit is turned up or off.

I service the Katy, Texas area.

Did the HVAC company mention anything about the refrigerant level being low and a possible leak? This could cause the problem you are describing. On a hot day measure the temperature at a supply vent and at the return. The difference should be in the 15-20 degree range. If it is less then that is a problem and likely a sign of low refrigerant.

Is the duct work in the attic? If so go in the attic and look for any ducts which have have tears or bad connections. You could be losing a lot of cold air in the attic.

I am wary of a company who offers no advice other than a total replacement. A 13 year old heat pump still have some years left. You could get a second opinion if you are not ready to spend the money on a new system. However if you plan to live in this house another 5-10 years then a replacement is the better option.

Thanks for asking. The refrigerant levels were good and they inspected the attack and found no issue. I agree about the new install and I think the service tech did too. He mentioned that it was operating within normal parameters. I asked about a new system and of course was shocked by the approximate pricing. I should have also mentioned that we've lived here for less than a year. Still getting to know our system. I had an oil burner and central AC in the old house. Separate systems and more basic.

How much insulation do you have in the attic and is there good ventilation? Spending money on improving the insulation and reducing the heating and cooling load is a better investment than replacing the equipment. How large is the second floor and what is the size of the heat pump? It is possible the heat pump and the back up electric strips are undersized. Look into the insulation first before making any major investment on new equipment.

It's a tall order asking opinions on replacement from people who don't have benifit of testing the system for themselves. There's a number of reasons that can cause your complaint. If the service and maintenance has all been done by same contractor,I'd get a secound opinion before replacement. The key is hiring someone you trust.

Good point, Klem1.