I'm building a new home in west central Indiana. My home is stick built, 2500 sqft single story, and full (partially finished) basement (10 inch poured walls) totally underground, total 5000 sqft. Blown cellulose insulation, R38 ceiling, R15 walls. Pella Low E argon filled windows, and full brick exterior. I've gotten two quotes for a geothermal system, but both estimate very different heating and cooling needs. quote #1, 3 ton horizontal closed loop, two stage compressor, variable speed blower fan, electric backup heat, heat 3.59 COP, cool 15.6 EER, 60,000 Btu/hr heating load, 33,000 Btu/hr cooling load, heat,cool,hot water-$644+$115+$217 = $976 annual, average monthly cost $81, quote #2, 4 ton horizontal closed loop, two stage compressor, electric backup heat, heat 3.35 COP, cool 16.91 EER, 91,000 Btu/hr heating load, 47,000 Btu/hr cooling load, heat,cool,hot water-$1126+$209+$288 = $1623 annual, average monthly cost $135, The initial total costs of the systems are pretty close. However, the anticipated operation costs are considerably different. Obviously, quote #1 looks the best with it's lower operation costs, but is the 3 ton system large enough? Please help with comments and suggestions, Thanks.

The lower operating costs of quote one appear to be somewhat predicated upon a substantially lower load calc.

For $50 you can download and use for a limited time HVAC-CALC, a load calculating software package. My gut reaction is that 3 tons might be a bit light for the described house, but there are many variables not covered in your initial post, such as amount and orientation of glass, so my gut could be wrong, and internet advice is typically not as good as work by a good contractor whose boots are on your ground.

Check also summer and winter indoor and outdoor design temps applicable to each quote.

I heat, cool and heat water for a 3400 SF house in north Florida using a 3 ton unit for well under $500 per year, so I can say that done right, these systems can work REALLY well.

What pcrcent of the heating requirement do both suggest they'll cover?
joe

If you need another guy to give you a quote, I can give you my installers contact information. I have only had my system since march... our electric bills are around $200. We are a total electric house.. and if my wife didn't have the temperature set to 69 degree's that would probably lower that electric bill.

Unless they are willing to guarantee them (which they won't), I wouldn't put any weight on their anticipated operating costs. It wouldn't surprise me at all if the second system would actually have lower operating costs - bigger loop and better cooling performance.

Sorry guys, author has not answered my question after 2 weeks, I think you are talking to yourselves.
J