We to have a geothermal (5-ton closed loop) conditioning 3600 square feet. I have a Harman P38 in the basement / family room (yet to be finished). In our case the idea of having the pellet stove is not to save money but to have a backup system (powered by a pure sine wave generator) during our winter-time power-outages. Also it works extremely well with the geo in single-digit/sub-zero conditions. I will never be without a pellet stove.