What is the advantage of a smart thermostat vs automating the AC in home assistant?
I use a smart one, but i still use HA to âoverrideâ it, f.e. when I leave the house, HA will turn the thermostat to âawayâ, regardless of its program.
Also when i come home earlier then expected, i can switch it back to âhomeâ from HAđ
Reliability and redundancy.
I have three smart thermostats which connect to the manufacturerâs cloud. Normally I hate cloud solutions, but Iâve come to accept this as a good option.
The thermostats have all the âsmartsâ internally. Theyâll continue to work, and run pre-set schedules, even if the LAN or WAN are off line.
They arenât impacted by any HA updates, breaking changes, hardware failures or bugs.
Yet, I can still control them through HA. I rarely use the manufacturerâs app or web site, but itâs nice to know that I can, if HA isnât available for any reason.
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Indeed if you want to have a thermostat work independently from other connected devices (aka servers - no matter other peoples one in the 
s or your locally owned one with home assistant) you need to have the thermostat function locally on your device.
The good thing is that a esphome based thermostat can exactly deliver this without being tight to any manufactures cloud (they are the servers from other people). Depends on some one needs ready made devices are available but itâs also possible to build dirt cheap DIY solutions which are reliable and work independently. The first class 
local push communication with the ha integration will be the cherry 
on the cake 
Good points. I think today Iâd look seriously about an ESPHome roll-your-own thermostat solution. It ticks all the boxes I mentioned above, without any manufacturer cloud.
That said, my off-the-shelf smart thermostats were surprisingly functional.
They donât just mechanically come on at one temperature and go off at another. They start with a target temperature and a target number of times to cycle the heating or cooling appliance. Then they estimate how long each cycle should last to keep the temperature at exactly the set point. There are no temperature swings within some high/low range like âdumbâ thermostats.
I couldnât really justify the time to code something that complex. Does the ESPHome thermostat code contain logic like that?
Esphome can do anything, but you need to program it accordingly, which is not âout-of-the-boxâ
Have a look at esphome thermostat
You either use Esphome autonomous, which does involve quite some programming if you want to set it up as you mentioned, or you use it in combination with HA ( and control/program the thermostat for HA)
As a side option that you can also control the esphome directly through its own web interface
Note that the esphome is not self-learning 
Are there smart thermostats that can send their commands through home assistant instead of wires?
I have a âtoonâ, it normally communicates through the cloud, but i rooted mine, so it communicates directly with HA (i donât like clouds, whever you really need it, it doesnât work).
it can do both wifi as well as lan
This almost sounds more like a PID controller than a âclassicâ or âdumbâ thermostat. Still the thermostat in esphome has quite a bunch of options and probably itâs possible to achieve such a behavior maybe by just tuning the Controller Behavior and Hysteresis? 
I mostly (almost exclusively) use my esphome thermostat through HA (control/program the thermostat in HA while the logic is on the esphome device 
for the mentioned reliability and redundancy).
I think this is essentially what I do with the esphome thermostat. Just ânativelyâ controlled in/from HA: 
Iâve never really considered self-learning to be all that beneficial. I donât really follow a schedule. If I did, I certainly wouldnât want some Big Data company monitoring it.
A typical smart thermostat sends commands to the heating and/or cooling appliances via wires. If it has some wireless connectivity, such as WiFi or Zigbee, then the settings on the thermostat can be controlled wirelessly, either through HA, a local hub or some cloud server.
After my last post, I did some reading on the ESPHome thermostat. I donât see anything about what Honeywell calls Heat Cycle Rate. As I understand it, the thermostat attempts to cycle the heating or cooling system âXâ number of times per hour. âXâ is a number you set by selecting what type of appliance it is. Obviously that requires it to calculate how long each cycle should last.
Heat in my climate is critical. Failures could result in burst pipes, making the house uninhabitable. Smart thermostats are inexpensive, reliable, and are programmed by experts to handle all the calculations needed, independently of any other hardware or software. And I can control them through an HA. That value is hard to beat.
Iâm still a tinkerer at heart though, and enjoy these discussions on how to build a home-grown solution!
While not prominently mentioned in the link I guess this is probably some proprietary âmagicâ honeywell does. 
And it even mentions:
Every heating system type will deliver heat to the house at a slightly different rate.
Maybe not only slightly different but actually different. Also the temperature changes (not only the temperature changes on a hot water tank which might feeds a heating cycle for radiators for example) can play a big part. 
So it probably depends a lot on each and every setup and maybe also individual habits. If people for example opening windows regularly for fresh air (and getting rid of humidity) it might be that there are more heating cycles. Also they depend a lot on the controller behavior and hysteresis linked in my last post. Depending on the setup and possible mixing and other pumps some ones mileage probably greatly varies. 
That gave me a good laugh 
While that certainly isnât true for all commercial products out there for sure the worst implementations I personally came across were the ones from such âexpertsâ 
Itâs a sword with two sides I guess 
⌠If you own (or buy) such a ready made product you need to âtrustâ that it does itâs job because one (beside owning the hardware) normally has 
influence on the software. Also hoping that potential bugs get fixed and that product gets care for the life cycle one intends to use it is mandatory - because typically âguaranteesâ from manufactures normally are only on paper and rarely more than a couple of years. 
That said I personally prefer not only owning the hardware but also the software which allows me not only to fix potential bugs in the future but also extend functions actually which commercial solutions out there only give me for more cash 
I, too, would prefer to own and control the hardware and software. I hate cloud solutions. So I wonât disagree with anything you say.
What I can say is that I sleep well knowing that the hardware and software keeping my pipes from freezing, and keeping me warm, was designed by a company which has been doing this stuff a very long time, and is very likely to be around for longer than I will.
It would never even have occurred to me to develop a feature like trying to keep the cycles per hour as close as possible to the ideal for the type of heating system I have. Iâm sure there are other features my thermostat has which Iâve never heard of.
The folks who developed this simple home thermostat (which sells for under $100) have decades of experience controlling the most complex heating and cooling systems in the world. Iâm OK with admitting they know more about this subject than I do.
Where I think weâd agree is about the new tech companies jumping in to make thermostats. They have no expertise in heating or cooling, and they are prone to dropping product lines on a whim. They market features like âlearningâ which nobody asked for. They exist in a fashion industry where the customer is expected to dispose of their hardware after a year or two, in favor of the latest model.
I am aware that typical smart thermostats send commands to the AC via wires. I was wondering whether there is a solution that avoids a hole in the wall.
Guess that all depends on your setup? I for example also make use of esphome devices to control my esphome thermostat while HA is the âman in the middleâ.
So the data flow is something like this:
Controller (esphome) 
â WIFI 
â HA 
â WIFI â Thermostat Relay (esphome) 
and the esphome module you can put near the heater, provided you have wifi coverage there.
ps: you donât need HA, any webbrowser will do