"is_using_emergency_heat" Always Returns False


I’ve noticed that is_using_emergency_heat is always returning “false” for a heat pump even though the Nest Thermostat device is sometimes switching to AUX heat for periods of time on very cold days. Has anyone else seen this?


This occurs on a few of the API values… is_online is another


Yes, I see the same issue - is_emergency_heat never changes from false.


So you have it installed and configured as described here, but when Emergency Heat is actually running is_using_emergency_heat returns false from the API for that thermostat?


That is correct. The thermostat displays ‘Aux Heat’, yet the API always returns false for is_using_emergency_heat. It is installed correctly as the emergency heat is actually on and working.

In my case this is a Nest learning thermostat.


Messaged you separately.

Is anyone else having this issue currently?



Thought I would check in on this. Any progress on getting the is_using_emergency_heat status to report accurately?



@jbumgardner Could you explain what is_using_emergency_heat is supposed to indicate exactly? I know some thermostat configurations have an emergency heat mode, while others have AUX heat and dual fuel have ALT heat. Are these conditions related? How does one detect AUX and ALT heat modes in use?


It should represent the emergency heating function on the thermostat, not auxiliary heating. It depends on what features your heating system has and how you wire up your thermostat. It’s explained here: https://nest.com/support/article/What-s-Emergency-Heat-and-does-Nest-support-it


@jbumgardner Thank you. That’s helpful.

Can you explain how we can see the use of AUX heat and ALT heat?


Beyond the base HVAC modes (heat, cool, heat-cool, eco, off), all you can see is if emergency heat is on or not with that other flag.

If it’s not detailed on the Thermostat reference page, it’s not supported in the WWN API.