Ecobee via Homekit Integration - how to set Aux mode?

I think this question relates specifically to using Ecobee thermostats via HomeKit Integration vs. via the Ecobee integration.

I recently added serveral Ecobee thermosats. The Ecobee Integration was not an option for me because of Ecobee’s apparent shutdown of the developer program as a way to access their API.

In my setup, the thermostats control Carrier heatpump systems with gas backups. There are certain situations where I may want to direct the systems to run off gas - for example, when I have an electrical outage and am running on generator.

There are two levels where Ecobee seems to give me some control over this. One is buried within the “installer settings” of the thermostat (afaik accessible only directly via the screen interface of the thermostat). The other is by switching the thermostat to the mode called “aux”. This latter option is available via the Ecobee app, but afaik is not available via Home Assistant using the HomeKit integration from Home Assistant.

Ecobee modes for my unit are {Heat, Cool, Heat/Cool (Auto), Aux, and Off}. Confusingly, the device page for the Ecobees in Home Assistant has a pull-down menu called “mode” but it does not actually set the thermostat mode. Instead it sets what Ecobee seems to correspond to what Ecobee calls “comfort settings” (by default {home, away, sleep}).

It seems using the dashboard interface, there is a button I can click that lets me select four out of these five modes, but not aux. Doh! So close.

So does anyone know of a way to switch my Ecobee thermostats from Home Assistant to switch to “aux” mode? This seems like an important gap in functionality when using Ecobee to control a heat pump system.

I have a multistage heat pump with aux heat and ecobee premium also. I’m no expert but I have not found any way to turn the aux heat on manually.

I did file a WTH for better heat pump support in the thermostat card and showing different stages including aux.

I also looked at Apple’s homekit docs but couldn’t see anything related to the thermostat entity that supported stages.

That said, happy to be proven wrong by someone more knowledgeable!

Glad I saw this because I was headed to the same place with heat pumps if I could figure out how to configure the Ecobee in HomeKit without any Apple devices (I’ve heard this is theoretically possible). My first problem is that the weather data provided to the thermostat is horrible by either being off by up to 8°F or when having Ecobee switch it to an alternate weather source I found it was more accurate, but the update frequency was terrible (I saw 9+ hours between updates). My thinking was to try to either get API access or somehow use HomeKit just via Home Assistant. Now it sounds like that won’t work either giving me AUX control. I’m quickly realizing the Ecobee just might not do the job I want and I’ll look at some Honeywell models that have wired temperature sensors with some models also having wireless temp.