This is my first post, and I am a relatively new member. We are in the process of planning a new home (conventional framing) and are considering going with a geothermal system for heating and cooling. I have two bids from prominent local (Garrett County, MD) HVAC contractors, and to say that they differ in terms of approach and proposed cost would be an understatement. Specs on the house (summarized below) were provided to both. Contractor 1 recommends a 3 ton Carrier system and prices the job turnkey at $22,557 plus wells (about another $7,500 for this system size). So about $30k total. Unfortunately, this firm did not account for the basement (full unfinished) or the upper garage (see specs below). Contractor 2 recommends a three-zone system with three GSHPs (one 5-ton, two 2 ton-units), with an equipment cost of $32,365 (heat pumps, auxiliary unit, duct work, controls, etc.), wells cost of $18,660, and labor, permits, etc. of a whopping $24,696. Total bid comes to $75,721. Contractor 1 has clearly under-scoped and underbid this job. But contractor 2's bid, while comprehensive, seems completely insane to me. I'd appreciate the views of any experienced geothermal system designers or installers out there. And if anyone is interested in and capable of doing a job in western Maryland, let me know. House specs follow: The house will be on a full basement with 9’ ceilings, which will be unfinished for now. That said, we will want to have the capacity to heat and dehumidify the basement in the future. We also will have a two story garage, with the upper floor finished (about 850 square feet), which will need to be conditioned, as well as a mudroom of about 70 square feet connecting the house and garage. The dimensions of the house are 28’ deep by 48’ wide. First floor ceilings will be 9’ and second floor ceilings will start at 7’ on the front and back of the house and rise to a peak (along the center line of the house) of about 14’. The second floor will have rooms throughout except for a hallway and railing overlooking the family room in the center. The garage will be 26’ deep and 35’ long. I expect that the first floor will be finished (drywall) but not heated, and the second floor will be finished with 7’ wall heights front and back and maybe a 12’ height along the center. We will have Energy Star windows and doors throughout, with most glass on the back side of the house, which will face due southeast. The back will have two glass French doors (80” tall, 6’ wide) and a combination (fixed plus two side double-hung) window about 5’ 6” tall and six feet wide on the first floor and combination windows of the same width but 1’ less height on the second level. Center rear upper level will have three 3’ x 5’ picture windows. Sides of the house will only have double hung windows (3’ wide) of about 57” height on the second floor and 1’ 8” by 66” in the first floor master bedroom. There will be two narrower first floor windows on the right side and one wider window on the left side of the first floor, and four second floor windows, two on each side. The front of the house will have six double hung windows, three on the upper floor (32” wide and 40” tall) and three (32” wide and 54” tall on the first floor. The second floor will also have a small fixed accent window 3’ or so in diameter. All dimensions are nominal, so glass area will be smaller. We will have a 36” by 80” fiberglass front door with two narrow sidelights. Walls will meet current code of R-19 in the walls and R-38 in the roof. Any reactions or wisdom you might care to share would be much appreciated.

I can't / won't try to take a verbal description into load calculation software, besides which fact a load calc ought to be worth about $200 or so. Any serious bidder should do one or at least plan to do one if awarded the job. A competent contractor may not want to share it with the HO with the bid out of fear it being shopped out to a lazy low bid hack house.

That said, my gut reaction from skimming your post (Consider several short paragraphs rather than one long in future for readability) is that contractor one may be closer to the mark. A slightly undersized unit is likely to be more cost effective than a way oversized system.

Given that this is new construction you might want to do or get paid to be done a load calc conforming to ACCA Manuals J and D.

You might also decide that getting air to and from the 2nd floor of the garage via the mudroom may be difficult enough that a small separate system such as a mini-split heat pump might make more sense for that zone.

Looks like 3400 SF or so,
I don't know how MD compares to my area but I suspect it's warmer. Off the cuff i suspect you need 3-5 tons but couldn't say without the manual J heat loss/gain calc.
Keep getting estimates.
And by the way....Most basements add load to the ductwork passing through unconditioned space or add similar load to condition. IOW conditioning or not conditioning the basement adds about the same amount of BTU's to the load (within a few thousand).
joe

The heat/loss figure is more important then the size of the house. It's possible to have a much larger house with a lower heat/loss than a smaller house with a higher heat/loss. This is why installation is so important.  It's possible to get away with a smaller system with enough installation, seriously consider foam installation such as ICYNENE^®

psoyka, I agree with TechGromit, make your new house like a cooler with closed cell spray foam. I've been going to Deep Creek since 1991 all 4 seasons (Aunt has a house not far from Zedock-miller road) but this is a vacation houss. This house does not have AC, electric baseboard heat ($$$) and a wood stove with blower. Unlike my part of Maryland (all clay when they drilled) that part of MD (just 14 miles from WVA) has a lot of rock. As most of the houses in Garrent Co are on Well water there are a number of drillers but the only one I know that does Geo is Waynes based in Cumberland. Did you say if this was a full-time hosue or vacation? CH