Comment by cmui

I understand the concern around lock in. There is a technical hurdle to optimized thermostat <--> variable speed heat pump interop. You have to turn the temperature error between setpoint and actual temperature into a compressor speed command and also factor in behavior such as defrost, compressor cycling limits, etc. So you have to have a communicating thermostat to fully utilize the efficiency of these variable speed heat pump systems, not just a collection of analog on/off wires.