That is a good point - I was told the same thing, in the north it is much harder to heat with geothermal than to cool so system must be designed for heating loads, not cooling. I was also told my system was designed for -20 degrees F and should not require any supplemental heat down to that temperature, especially after a few summers of cooling which is storing heat in the ground. After this summer should be good to go for a cold winter! It also seems like geothermal gets better after a few years when everything settles into a cycle. Jim at Dawn | 
Geothermal horizontal loops in a drought?
