Geothermal?
We're on a natural gas HVAC - big central air furnace unit in the basement, big AC condenser outside, connected to central air. In a region where lows can hit -30C in the winter and +30C in the summer - a system like this is critical. On the hottest days, I wish I had more horsepower in my blower motor to push the cool air upstairs. In a 98 year old house, we have a lot of heat/cooling loss. Modern windows, R40 insulation in the attic, but not a stitch of insulation in the walls!
Also have two natural gas fireplaces in the house. Makes it nice and toasty on cooler days and don't have to run the furnace at all between 0C and 15C.