Is this a 2300 sq. foot single story house with another 600 sq. feet above the garage? Is the 1700 sq. feet all below ground? The HVAC contractor must do a heating and cooling load calculation. If he refuses find another contractor.

You have to close on the house by December 31st in order to qualify for the 30% tax credit. There is a chance the tax credit is extended by Congress into 2017, but so far there has been no talk about it. The tax credit does not cover the duct work or the hot water heater.

I don't think the propane furnace and AC, or an air sourced heat pump would cost more than a geothermal system after the tax credits. Get some quotes to convince yourself either way.

2300 sq foot main floor with 600 sq ft area above garage (2nd floor), and 1700 finished part of basement.

I'm sure they will do a load calculation on a formal proposal. This was just a budgetary quote to see if it was even remotely feasible to consider at this stage. I think it was more a quick and dirty level quote. However, if experienced folks see this and right away say, "hey that is way undersized!" or "that model isn't what you want", then those things are helpful to consider moving forward. If they had said $75k, then I'd know it's crazy to even pursue. That's what I was really trying to gauge.

We want to consider geothermal as an option, but much of that will depend of the tax credit being renewed. We wouldn't even start building until later this Fall, so there would be more time to see if it is extended.

ASHP and/or propane are definitely cheaper, but if you get the tax credit it isn't a staggering difference. I'm more concerned about ASHP performance at lower temperatures here in PA (requiring heavy backup use) and the propane, while fairly cheap now, has been very expensive in the not so distant past. It's not only about the upfront costs. We will definitely get several quotes, including ASHP too.

I would think 4 tons of cooling would be plenty for 2300 sq feet given your location and insulation values. I would not be surprised if the load calculation showed between 3 and 3.5 tons. The heat pump has to be sized for cooling and not heating.

There are heat pumps that have good performance at low temperatures. You can also get a dual fuel system which is a heat pump with propane back up.

Are you in SE PA or Northern? Low humidity in winter is greatly due to air leaks. I have a hard time believing that you will need a humidifier in a new, well-sealed home. I'd skip it and leave provision to add it if you find it necessary after a year or two. It seems like you should be able to heat and cool the area proposed for a mini split from the ground source heat pump in some way, but maybe it ends up too expensive by comparison. I am thinking circulating hot or chilled water.

Price ‘seems' good.

Why can’t the geothermal condition the
space above the garage as another zone?

SR

To answer a few questions in combo here:

1) I'm in South Central PA, almost in Maryland actually

2) As for not doing another zone above the garage? We definitely can, and should consider it. In our current house that's a real problem area and it was always much hotter or colder than the rest of the house, so we had a dedicated mini-split installed up there, and it's been great (was like 26 SEER thereabouts too, so it's been fairly cheap too). I just thought maybe it would be more cost effective to do that, but maybe zoning and proper sizing would allow us just to use the same source everywhere? We will definitely ask for that as option as we proceed.

3) The 4 ton would be for 4000 sq ft (main floor and finished basement). I'm thinking 2 zones they mention probably was preliminary until they did detailed calcs, but we'd want more for sure. I was just wondering if a 4 ton could really cover that much over two floors?

I assumed that the mini split was installed because it is very difficult to get ducts to that location. My suggestion assumed that you could get chilled or heated water there much more easily and install another AHU and fluid-air heat exchanger. If ducts could be run to the area above the garage, in the hands of a good system designer and installer you could have good heating and cooling there. It might, indeed, be more cost effective to install a mini split than the other two alternatives.