Heat pumps do come in half ton sizes. You must look at the net BTU your old one was putting out and the net of the new one at the same design temperatures. Also you don't want to end up oversized when the insulation is added.

"The two contractors below came up with a 2.5 size but heat pumps only come in whole sizes. Am I over sizing the unit if I go with the 3 ton heat pump?"

The heat pumps you were quoted are 2-stage models. All 2-stage heat pumps come in whole ton sizes. You would have to get a single stage heat pump in order to get the 2.5 ton size.

I am in central NJ so my climate is very similar to yours. Did you review the load calculations? Is the 1800 sq. feet all on the second floor below attic space? Given attic poor insulation (R19 or less?), the 2.5 ton may be slightly under sized. In my opinion I don't think a 2-stage 3 ton heat pump is over sized. We would have to look at the data sheet, but most likely the lower stage will be less than 2.5 tons.

It is difficult to comment on the price because of the required duct work. It sounds there is a lot of labor involved in the new duct work and attic installation. Contractors don't like to break out line item cost. Getting one price is very common. You have gotten 8 bids, so you compare prices. You did the right thing by rejecting people who don't even go into the attic.

The answer you other questions, I think 2-stage equipment is worth the extra money. It is going to do a better job of lowering the humidity in the summer. It should also be quieter when running on the low stage while you are sleeping.

I think suspending the air handler from the rafters is the best way to minimize noise. I don't have experience with attic installed equipment, but it seems logical you would cut down the vibration from the ceiling.

You want R8 insulated ducts in the attic. The main duct should be metal and all joints should have mastic. The flexible ducts should have no kinks. If it looks bad to your eye then it is probably bad. You are doing the right thing by investing in improved duct work.

I like Carrier over Lennox. You also want a 2-stage thermostat. Find out the model number and make sure it is in the quote.

For your location, I would not have a HP system that did not have electronic demand defrost. Neither the Lennox or Carrier offer this feature.

New Heat Pump System

Here is my general spec sheet for new system.

both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF

best matching VS air handler

full BTUs in both cooling and heating for your rated size

R-410a refrigerant(same as Puron)

scroll compressor preferred

electronic demand defrost preferred

thermostat with "dehumidify on demand" feature

staged backup heat strips depending on system size

new and correctly sized refrigerant lineset

10 yr warranty on parts and compressor

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

My personal recommendation is Trane/AmStd and Carrier/Bryant.

Depending on your location, I would not purchase a new system that did not have electronic demand defrost.

IMO

Thank you all so much. This is from what I can tell a complicated job and so many things to think about. Electronic demand defrost is one new important issue I had not thought deeply about and only 1 contractor actually discussed with me. The variation in contractor bids is amazing. Most appear to be 'drive by' estimates few (very few) actually do a thorough job of evaluating and educating. I appreciate you sharing your expertise and hopefully I can pay it back on another topic at another time:)

These prices are not inexpensive. I would not have the Lennox period. I recommend you get a price on Trane XR16 and identical model from sister company American Standard.

IMO