What is a heat pump with auxiliary backup heat?
Considering this, what is auxiliary heat on a heat pump?
Aux on the thermostat stands for auxiliary heat. Auxiliary heat is the electric heat strip in your air handler that is supplemental heat. Auxiliary heat/ Emergency heat help the heat pump keep up when cold outside or the temperature differential on the thermostat is large.
In respect to this, why does my thermostat say auxiliary heat?
Turning your thermostat to “heat” came with an unexpected “AUX” function appearing. The “AUX Heat” mode is usually an indicator that it's freezing outside, and your is heat pump is using a secondary backup heat source – your auxiliary heat—to keep your home at your set temperature.
I guess the only difference is that AUX is an 'indicator' on your thermostat that you are running the heat strips when the switch is set to HEAT. Emergency Heat is just the switch setting that will turn off the heat pump and only run the auxiliary heat. Emergency Heat Indicator only when in Em. Heat Mode.