Where I’m at, the temps flip-flop day to day, even hour to hour. In the morning it’s 35° outside, and by evening it’s 79°. I gave up keeping up with the temps and shut my unit off for the time being.
My question is why can’t HVAC units be programmed to say that if the outside temp reaches n° and the inside temp reaches m° cold, turn on the heat; conversely, if the outside temp rises to n° and the inside temp reaches m°, then turn on the AC?
My thermostat already knows the outside and inside temp, but I still have to manually switch it back and forth. I want a system that I can just set it and forget it all year round.
I just set my ecobee to “auto”; the only possible inconvenience is the required gap between heating setpoint and cooling setpoint so it doesn’t constantly flap back and forth as a result over overshooting the setpoint. I have the gap set to 3 degrees and tend to shift it up and down seasonally (e.g. heating setpoint at 72 and cooling setpoint at 75 in the winter, heating 69 and cooling 72 in the summer)
Insolation and air infiltration based on wind conditions likely affect loss as much as outside temp, and the thermostat doesn’t know that (it could presumably learn to relate time of day, cloud cover, day of year (solar angle), wind conditions with that - but it would take 2 years to learn and its response would be opaque - most homeowners want bang-bang control since they understand it.