TL, DR: I want to emulate Ecobee’s Follow Me feature using sensors and automations, but I need help selecting a method to tell the thermostat to turn on/off. That may mean I need recommendations for a new thermostat that can do what I want to do.
I’m in the market for a new thermostat for my apartment to replace my existing Nest. The Nest is mostly working for us, but in the years since purchasing it, I’ve stood up a Home Assistant config that the family now can’t live without and I’ve learned more about the need for local APIs. While doing research on which thermostats Home Assistant community folks recommend, I took a dive into the Ecobee thermostats because of their Homekit compatibility.
One feature of the Ecobee that is interesting to me is Follow Me because it might solve a problem I’ve been having. Follow Me is a feature that helps set the correct temperature based on room occupancy and sensed temperatures in each room. It depends on multiple temperature sensors, occupancy sensors, and some logic that selects, weights and averages temperature readings. This is interesting to me because when room doors are closed, our air conditioning system will make some rooms much colder than others. Today, our fix is to manually prioritize which rooms should be at the optimal temperature and adjust the thermostat’s set point up or down to get the right temperature for the prioritized room. I understand that the Follow Me feature won’t fix the problem of an unbalanced HVAC system, but I like the finer control and automation this feature offers.
The problem is that the Ecobee sensors are overpriced, slow to update, and aren’t great occupancy sensors. The Xiaomi Mi 2 temperature and humidity sensors (after being flashed) are around $3-5 USD per plus another $8 or so for an Aqara motion sensor, while the Ecobee sensors are $40 a piece.
I’m now looking for a solution. I can work through building the automations and templates to derive the “weighted sensed temperature” and our desired temperature, but where I’m stuck is figuring out a way to communicate both to the thermostat. There seem to be three solutions that other folks like @swiftlyfalling have considered:
Set Point Method. This method appears to compare the desired temp and the weighted sensed temp and makes adjustments to the target temp on the thermostat. In other words, if the weighted sensed temp is 23, the desired temp is, and the temperature the thermostat is set to is 22, the automation ticks down the thermostat’s set point by some amount at some rate (a function of the delta between weighted sensed temp and the desired temp) until the weighted sensed temp reached 20.
My concern with this method is the possibility of short-cycling the HVAC system. It appears that Ecobee’s solution to this problem is to add both a minimum cycle time and an automation to slowly adjust the weighted sensed temp if a new room was added to the mix because its occupancy sensor triggered.
Thermostat Temp Sensor Override. Another method I’ve read about involves overriding the thermostat’s sensed temperature with the weighted sensed temp. It involves overriding the thermostat’s internal sensor with the weighted sensed temp. There appear to be a few different ways to do this, ranging from creating a virtual sensor that’s accepted by the thermostat as a remote sensor to wiring a programmable device that can produce electrical signals to communicate the weighted sensed temp.
One user reported success using a Go Control Thermostat. I’m not currently running any Z-Wave devices at the moment, so we’d need to add that capability to our system. It’s also an ugly thermostat to me.
Build Your Own Thermostat. The last solution I’ve seen is to build your own device. Although I’ve looked into building my own thermostat using relays, my apartment is a rental and I won’t have an easy way to make the thermostat look OK on the wall. I also need to be able to provide others in the house the ability to adjust the thermostat manually as my “fail elegantly” plan.
I have two questions for the community:
- Are there other methods that I’ve missed?
- If the answer to 1. is no, then it seems the most elegant solution for me is finding a thermostat that permits a Home Assistant-generated remote sensor to override the internal sensor. Is the Go Control the only thermostat that integrates with HA, permits override and is not cloud-dependent?