I really love this post. The author did a great job with their writeup, and that probably came from a clear presentation.
I'm fascinated by your approach where you used your own temperature and humidity monitors. Apologies if this is in the links in the article, but I wondered how you controlled your heating unit. The reason I ask is that I have a nest device talking to my AC unit, which means I'm locked into the Google ecosystem. It works well, but it doesn't connect to the Home Assistant system for everything else in the house. I would like to remove the Nest dependency, or at least have multiple ways I could start optimizing the power utilization of my AC unit.
Thanks. The smart heating device in question is one that is fairly popular in Ireland, but I believe it isn't sold elsewhere. The brand is Climote (https://www.climote.ie/).
As part of the service, this controller gives you the option to send commands through an app, or by sending SMS (the device comes with a SIM card and gets its own mobile number). The commands would allow you to ask if the heating is running or not, to turn the heating on or off, and so on.
I first implemented the SMS interface with Twilio, but then found that the number of texts you can send to the device is capped. I don't remember what was the monthly allowance, but I reached it in a few days after querying the device every 15 minutes or so 24/7.
I then found a project on GitHub with the reverse-engineered API that the phone app used to send commands. So I then reimplemented the command logic using this API to be able to talk to the controller without limitations.
I'm not familiar with the Nest devices, but I'd suggest you do a search on GitHub to see if someone figured how to reverse-engineer its API.
Nest devices do integrate, sort-of, with Home Assistant. But, the process is to create an "app" inside the Nest + Google home automation ecosystem. It is an absolute mess and there is nothing to be gained by going into that Mordor. I tried to get it working, and gave up, but I would much rather use a device that is "hackable." That device you mentioned looks great, and does not appear to be available outside of Ireland, as you noted. But, I'm going to use that as an inspiration point and see if I can find something similar. Maybe that manufacturer has awareness of a US-based device provider, I'll contact them.
Really appreciate you sharing this work, really fun stuff!
If you're in north America (probably elsewhere, but I can only say for NA) then changing the thermostat is super simple to do. If your system is 24v, which is very likely, then swapping the nest device for something better isn't too complicated. I can't provide a brand recommendation, but I'd find a thermostat that supports homeassistant and has a reverse engineered API available.
Directly controlling the HVAC with a relay board would also be very doable, but is a more involved project.
I installed my nest, and it was indeed very simple. And, it appeared to work with Home Assistant, but like I said, the devil is in the details. It was a very frustrating experience.
The problem is that if I look here I cannot tell the first thing about which device is supported and how well. HA does not have a great filtering system.
https://www.home-assistant.io/integrations/#climate