A Waterfurnace GeoPro dealer proposed a 7 series NVV036 for a tri-level residence with a heating load of 51,300 and a cooling load of 31,500 for about $32,500 with the optional variable speed flow center, 2 wells @ 280' each, and 0.40 grouting. As an alternative, he proposed a 5 series NDV049 for $3500 less. Since he was offering a 10% discount w/o the financing option, that'll pay for the 7 series, which is preferred. I was told that the NVV036 is a 3-ton cooling/4-ton heating unit. Based on advice from gmith (iirc), I ran the numbers on Loop Link, which I never used before, and found that the NVV036 would provide an installed COPavg of 4.28 and EERavg of 25.5; or the NVV049, I got a COPavg of 4.95 and EERavg of 24.5. That's a big jump in COP for an added $3200 (for the 7-series NVV049 and 635' of boreholes); however, the dealer's data from GeoLink (4.23/26.1 for 7-series NVV036 and 4.26/31.4 for 7-series NVV049) showed no appreciable change. The elephant in the room is that the actual ceiling R-value is highly variable, so the heat loss/gain could be off substantially. I need to seal the deal ASAP. My questions: (1) can the 7-series NVV036 provide 4-tons of heating? (2) Will there be a big COP difference or not between the 7-series NVV036 and NVV049? (3) Should I go with the dealer's recommended 7-series NVV036 and 560' of boreholes or the 7-series NVV049 with 635' feet of boreholes?