I’ve been wondering where the break-even points will be for ground source systems, too. I was talking with an architect a couple weeks ago who has looked into that for several projects and didn’t find the number close to working out, but that was in Boston where the winter climate is nowhere near that extreme and the labor/land costs are very high and space issues meant they’d have to do the most expensive vertical boreholes.
10 years ago the average heat pump had a CoP of 3. Today they are 4 or a bit higher. Some ground source heat pumps have a CoP over 5. I saw one unit with 5.3. Of course, with a ground source heat pump, you can actually get that CoP when the outside air is -50C.
