I ran both programs and came up with wildly different answers. I am finishing my basement and adding heat to a bathroom that the current HVAC doesn't handle well. Both more or less agree on the cooling load but are off by a factor of 2.5 on the heating load. I have a master bathroom with lots of north facing double pane low e window area relative to the exposed wall space with about 88 sq feet above what will be a finished heated basement. The walls are 2x6 with some unknown amount of spray foam in them. The basement is a mix of exposed and underground poured concrete walls. As an approximation one room is 15x15 with two interior walls, one south facing wall completely exposed but under a deck and the other about half exposed and half underground. Each wall has about 12sq ft of low e double pane horizontal slide windows. The final area is roughly 33x14 with 3 interior walls and only about 8 feet of exposed wall. The exposed wall has one 36" door and another 12sq ft window. The exposed basement walls are again 2x6 with unknown amounts of spray foam with 2.5" of XPS on top of that. The buried portion of the 33' wall is 2.5" of XPS. Everything is covered with 1/2" drywall. CoolCalc says 9617 BTU heating while loadcalc says 22986 BTU. This is for a house in the Grand Rapids, Michigan area. The contractor is saying a 2 ton 3 head Fujitsu minisplit with a 7k head in the upstairs bathroom, a 7k head in the downstairs bedroom, and another 12k head in the large family room. That seems like overkill but if loadcalc is correct it isn't far off. If CoolCalc is correct then I am incredibly oversized.