[gorush]

Heat loss calcs required us to heat our garage as well as the house and shop in order to make the smallest heat pump efficient. We have a 3.5 ton heat pump and a 5 ton closed loop geo-field. We light the fireplace when we get below -10F.

[Myrddin]

My air conditioner condenser started life as part of a heat pump. Apparently it was inadequate as a source of heat for my 3500 sq ft house. By the time I purchased it, the house was heated with forced air/natural gas. The heat exchanger remains in place and functions as a moderately satisfactory air conditioner. Once the summer temps rise to the level of +86F at night/+100F daytime, we have to turn the air conditioner on. In winter, the wood burning stove in the family room can keep the gas heater in the off condition with a single log. That's good when the temps go subzero.