REPORT - Ground source heat pumps: Opportunities and challenges - David Petroy, NTS Energy

Over the course of the winter, as the home or building continues to pull heat from the earth, the earth in the vicinity of the borehole cools and its temperature decreases, resulting in lower fluid temperatures in the ground loop. [...] For a GSHP system for the same home, the cost of the heat pump equipment and pumps would be slightly less than the cost of the ASHP system – about $20,000. [...] The colder the accepted design temperature, the smaller the loop field, but the lower the efficiency and capacity of the heat pump system. [...] The table below is a specific example of the impact of the geology and location on the loop sizes for our models for three of the common ASHRAE geologic classifications for design.32 As shown, depending upon the geology, the loop field size (number and depth of boreholes) can vary by a factor of two. [...] On the Front Range the loop prices will tend to be in the middle to low end of the range, while in the high country they will tend to be in the middle to high end of the range.