What documentation should I ask for to compare geothermal bids for selection of a contractor?

I need a short list that won't blow me away technically, but should stand up to demonstrate that the contractor has considered the proper estimation methods and that the results match the system he proposes.

Also, what is reasonable for a large metropolitan area as far as asking for how many separate references of satisfied geothermal customers? Should I ask for phone numbers of customers who've had similar systems done by the same company installed for the last 2 years or 5 years?

How do I prove how many geothermal units the contractor has installed before? Is that excessive to ask for a long list of homes or names to prove the contractor's level of experience?

If the contractor recommends hiring a vertical bore driller or a horizontal ground loop installer so that the customer pays the driller directly, how do I ensure who is liable for making sure the proper design and functioning of the horizontal or vertical closed loop system? Do I also need customer references for geothermal jobs done by the driller regardless if they do a horizontal or vertical closed loop system?

How do I make sure that I get an accurate estimation of what my monthly kW power usage will be during the winter and summer months? I want to estimate time to achieve return on investment and I want to make sure I am not getting an underestimate of operating costs in terms of power.

All prospective bidders have seen the house, measured ductwork, room sizes, and reviewed the type of construction of the house, and are given information as to previous years annual oil consumption for forced air heat. All have also been given what my goals are for A/C in the summer and heat in the winter.