It depends on your skills and experience, but this can be done in another way that gives you many more options: use the Nest API's. I've written a bash script that can query these API's, and I can - for example - poll these API's to obtain the data from my Nest thermostat and do with it whatever I want. To give you an idea of what kind of data you can obtain, this is the output of my Linux command 'nest' (some data anonimized):
$ nest
The time is Sun Jan 8 15:23:35 CET 2023
You are in ******
Your Nest display is known as "******"
Humidity there is 53 percent
Room temperature is 18.23 degrees CELSIUS
Outside temperature is 9.18 degrees CELSIUS
Outside windspeed is 5.66 m/sec
Currently we have broken clouds
Wind direction is SSW (200 degrees)
Air pressure is 997 hPa
Desired minimum temperature 18.05133 degrees CELSIUS
Your heater is OFF
Have a nice day
$_
Note that the weather data is obtained by querying the OpenWeather API, similar to what the Nest itself does, as it has no external weather sensors.
Of course, a modified version of this script can be used to store your data in a database (whatever kind) and utilities like gnuplot might be used to plot the double curve etc.
Actually, I have roughly the same desire you have, but will also combine it with data on my gas- and electricity consumption.
But it requires sufficient Linux / bash skills. If you have such skills, you may consider checking out this link for some additional information, which should suffice to get you started.
