Would a window unit work for the basement? I have a 220V window unit heat pump for a 700 sq ft mother-in-law apartment out back and it works great in summer and in winter. Plus, you can install it yourself. FYI - heat pump efficiency starts going down as you start getting below 32 degrees. I live in south Texas so that is not a problem here.

I have a place in NE Okla that has a natural spring on it that flows around 5 gallons/minute of 65 degree water year round. I've been thinking of installing a 1000 gallon underground concrete tank downhill from the spring and keeping it filled by gravity flow. That would be the ground source for a geothermal system. I would put the exchange coils inside the tank. The water would run continuously into and out of the the tank and run on down the hill. The tank would also be used for house water.

Not counting duct work a 3 to 3.5 ton unit aught to cost in the neighborhood of $5K. Lot of variables though.

Dcomp

Your location?

Prices can vary from market to market and usually depend on competitive forces at work.

Basements properly insulated usually have very small heating and cooling loads if below grade.

My idea for comfort would be two systems; one for the basement and main floor possibly with zoning controls and a separate system for upstairs.

Depending on size of basement living space, I don't care for the suggestion of a window heat pump for new construction.

Last I heard, the tax credit for geo was 30% with no maximum.

IMO

The HVAC contractor is quoting 8.5 tons of cooling? How big is this house? What sizes are the proposed furnaces?

I am located in Maryland - Howard county. The house size is 5400 sql ft above grade and another 1300 sq ft basement. the credit I was referring to was regarding replacing conventional unit with Geotherm (no federal or state tax credit). I n short what would a conventional setting with above parameters what would it cost to put a traditional HVAC system including duct work. Is $20K-$25K sound reasonable or is it too high or too low.

Thx

$20k is on the low side. Builder basic in cheap area. More like $25 and closer to $30k if you are commutable to DC. I spent $20 in NC for 3 and 4 tons - Carrier Infinity for a smaller house than yours and basement would have added $5k.

In general, with access to NG in your climate, geo is hard to justify. With a tax credit, it can become a close to no cost option.