I have had 3 different companies come out to give me a proposal to upfit my 22 yr old house with Geothermal and all 3 companies have given me different size units and different number of well holes and depths, Iam ready to pull the trigger to get it installed but not until I get this resolved. I paid to have a company come out to a Home Performance Analysis on my home thinking that would give me the answer but really was good information for homework for me to do to make it more efficient and also gave a copy to the companies I was considering and they still said to go with what they originally quoted me so needless to say Im not ready to spend good money on bad until I feel satisfied with this painful project. Any help to the resolution would be GREATLY appreciated.

Have any of the companies provided you with a heat-loss/heat gain calculation for your home? A properly done calculation is the best/only way to know what size of system is required. This is something that is separate from what most home performance/ energy auditors provide.

Go with the company that can provide you with this calculation to explain why they sized the system the way they did. If you're unsure, have a heat loss calculation done by a qualified 3rd party. The cost of this would typically only be about 1% the cost of the geo system.

Unlike nearly every other type of heating system, geo is really expensive to upsize, yet there is still often a tendency to oversize for a particular project.

Pay most heed to the company(ies) that appear to have invested the most effort into a ACCA Manual J compliant load calculation. It may also be that some of the home performance analysis recommendations would be cheaper to implement, thus lowering the load, than going with an upsized system.

Check references and reputation of bidding companies.