I have a 3100sf house in West Michigan near Grand Rapids. I had a 4 ton Bosch geo unit install this spring after the heating season had ended. I knew the unit wasn't working right in November and the installer has been working on it since then trying to get it to run correctly. In stage 2 heating at 30°F outside air temperature the unit can't keep up with heating our house to 70°. We have been forced to run with the inline 9.6kW electric strip heaters just to keep the house warm. My last electric bill for December which was 6.2°F warmer than normal was over 4500kWh (3800 - 3900kWh of which is geo related). The calculated load would have had us using about 1600kWh for heating in addition our baseline usage is approximately 700kWh. Needless to say our current bill is as much if not more than I would have paid with my old single stage propane furnace. Our house has 2x6 walls with spray foam insulation and an unheated basement. There are a fair amount of windows but the installer took that into account with the software he used to calculate our heating/cooling load. There are 4 100ft horizontal loops (total of 800ft length) placed 5ft deep. We are getting desperate since we paid a boat load of money for the privilege having the same or higher utility bills. Does any of this make sense?