In my installations, which I swapped from Nest to Ecobee, the Ecobee 3 supports aux heat: https://support.ecobee.com/hc/en-us/articles/360010176991-ecobee3-Wir

In my installations, which I swapped from Nest to Ecobee, the Ecobee 3 supports aux heat: https://support.ecobee.com/hc/en-us/articles/360010176991-ecobee3-Wiring-Diagrams https://support.ecobee.com/hc/en-us/articles/360010176991-ec... https://support.ecobee.com/hc/en-us/articles/115000414828-How-to-minimize-the-use-of-auxiliary-heat-with-a-heat-pump-on-your-ecobee-thermostat https://support.ecobee.com/hc/en-us/articles/115000414828-Ho... Note that with basic Ecobee systems, you may have to purchase another adapter to connect to some systems. The Ecobee 3 (not Lite) I didn’t have to. https://support.ecobee.com/hc/en-us/articles/360028428931-What-are-the-differences-between-ecobee-SmartThermostat-with-voice-control-ecobee4-ecobee3-lite-and-ecobee3- https://support.ecobee.com/hc/en-us/articles/360028428931-Wh... I have a property with industrial boiler, heat exchanger, and a dozen independent zones w/ pumps, heat only, with particular needs to cycle pumps from time to time, keep active for minimum windows, etc. I also have a property with geothermal plus auxiliary electric. Of things I can manage from Siri, Google, and Alexa, both (only?) Nest and ecobee 3 were able to support these custom/advanced configurations, though I’d argue Nest was better with the commercial/heavy needs, both in the installer options available, and in service support. I haven’t found others that support these options that are also supported by HomeKit (Homebridge) or Home Assistant.