I’d like to measure the time taken for a temperature sensor to reach a particular value, hoping that I’d be able to cleverly turn the heating on and it would be warm for when we get out of bed, or return home for example.
So far searches have been fruitless, and before I go down the route of Python I wanted to see if anyone has been able to achieve this natively with HASS. Thanks for any tips!
If you live in an older home, that isn’t insulated to current standards, wouldn’t that time duration vary depending on exterior temperature? In other words, there’s no guarantee that increasing the temperature from 18 to 22 always take (for example) 30 minutes throughout the entire heating season. On very cold days it may take longer (due to faster heat loss).
Yeah this house is over 300 years old so I’m not expecting mega accuracy, more of an experiment. 
If you are using any of Home Assistant’s climate integrations to control your heating system, you can look at its history chart. It graphs the ambient temperature and the heating time. That should give you an idea of how long it takes for the temperature to rise.
It must be a PITA retrofitting smart switches into the castle walls 
Dunno, did you see the castle walls in “the man with two brains” ?
You’re damn right it is.
I have a house that’s about the same age. I tried something similar as you. Let’s just say it like that - I gave up.
Not sure what your house is made of, but mine is made of stone. Really thick (>1.5m thick at some parts) natural stone walls, held together with clay and lime as mortar. Upstairs, the outer walls are compressed straw mixed with lime in a wooden frame. The roof is poorly insulated thick natural slate. That gives some real interesting thermal behavior As Taras said, the outside temperature is vital. But not only that. These old construction materials typically have very high thermal inertia. So you have to consider the outside temperature development over several hours or even days. Then humidity. Due to the clay mortar, which is hydrophilic, the thermal transfer coefficients of the outer walls change with outside and inside humidity in totally non-intuitive ways. And not instantly, but slowly over several days, depending on how much it rained.
So yeah, fun… I now just have HA turn up the heat when I leave work and hope for the best 
Interestingly, the issue aren’t really the switches, but the cables… Thank god for battery powered wireless switches. This is a situation where smart switches aren’t convenience but a necessity:
As others have said, it is highly variable. You’ll have to get a feeling for it based on your own experience. A rule of thumb really.
You’ll probably get to know how long it takes on a cold day, how long it takes on a not so cold day. Then you can programme HA accordingly.
eg, if today’s average temp has been below 10 degrees, start the heating 40 mins before I am due to get home. If it has been above 10 degrees start 30 minutes before.
Some smart thermostats claim to “learn” how long it will take to heat up (or cool down) and start the heating system accordingly. Obviously that’s outside of HA, but most can be integrated into HA so you at least have monitoring and control, even if you still have dependencies on third party hardware and servers.
My house is “only” around 150 years old, but I feel your pain.
Thanks for the replies all! My conclusion at the moment is that this experiment is not worth the hassle. 
That’s a nice warm looking robe you have on in your picture. I guess you appreciate it on the days you’ve misjudged the timing.
As a start I think I might try to record some times to target against temp difference inside/out and see if predictable pattern. 12 YEAR old house(barely out of nappies).
Hey, did you figure out the time-to-target-temeperature thingy?
I’m looking to do the same somehow.
I just thought i’d ask before i dive in to my influx db historical data 
I’ve been keeping any eye on the time to target and the biggest factor is outside temp.
I’m in the process of building an external temp sensor(bmp280) based on Wemos D1 mini pro with 18650 lithium battery and 6v solar panel with protection charging/discharging. This will give me a better idea of what’s going on outside and in the future adjust heating accordingly. This has been a new rabbit hole to go down.
In the meantime I have set my heating schedule to bring my house up to 17C starting about 1hr earlier than regular target temp as I don’t know what the starting temp is going to be yet each morning. A little inefficient but seems to work.
I have replaced a couple of the TRVs with underfloor actuator valves controlled by sonoff Minis. They open the valve fully and then are programmed to shut off fully(about 0.5C) before target room temp to prevent significant overshoot. The other radiators then have a finer control to maintain target temp.
Lots of new things and words I should look into.
Thermostatic Radiator Valve right?
Had to look that up 
Could you give me a link to those?
BTW, I solved my outside temp need with a xiaomi zigbee temp/him sensor.
Hooked up in a protected spot outside.
(just an alternative if you decide not to mess with constructing it)
Underfloor heating manifold actuator 230v Normally Closed
The whole fun is making things yourself. My soldering is coming on nicely. 
