My system was installed in 2010 and works great; I' very happy with it. Lat winter I started to monitor the incoming water temperature and was surprised to see that (at the end of the heating season) the water temp and therefore the ground temp had dropped by 12 degrees. Monitoring summer temperatures showed the temp rose by 8 or 9 degrees. Everything I read about GSHP before install talked about using the "constant" temperature of the ground as a heat exchanger for the system so I assumed that the loops would be designed to return the water at or near the ambient temperature of the underlying rock. It seems that with the water temp dropping 10 degrees the system has to do more work to get heat out of the water and therefore is not as efficient at the end of the season as it is at the beginning. Would it have been more prudent to install additional loop footage? I live in Wake County in North Carolina and am using a Climate Master 27, 3 ton capacity and have two closed loop vertical bores, 270 deep and about a 100' run from the bore holes to the foundation wall. The bore holes were back-filled with bentonite grout. That gives me a total of 1,280' of loop.