I must be too old school because my first thought when i read this was “with an old solenoid lying around and a few lines of code, an AtTiny could strike a key on the bluetooth keyboard, waking the laptop!

have a look at Shelley smart devices. They have a wifi button that’s fully compatible with Home Assistant. Not the cheapest in the world but the quality is excellent. No Zigbee needed.

https://www.shelly.com/en

you might have to install OSMC in a proxmox virtual machine if you can’t do a bare metal install.

i’ve got one and hacked it with an ESP32. it’s awesome, but it’s not a CO2 sensor, it detects fine particles in the air.

do you have a gas meter? surely it would be simpler to capture the operation of the meter either electronically if it’s a smart meter or optically if it has a moving part or dial?

Even if your heating is gas it should be possible to disaggregate that usage by measuring the consumption over a minute or so.

I’ll take “what are circuit breakers for?” for $250 Alex

leave the switches in the wall but bridge the cable so it stays on irrespective of the switch position. or join the cables behind it with some terminal block

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