Industry standard current rating for thermostat relays

[LittleRain]

I am currently creating a smart thermostat for my home, and am thinking of maybe doing a small production run to sell.
Its a 24VAC system, which I measured about 30mA on the white heat wire, give or take.
The relay I used is more than capable rated at 900mA, but just to be safe I want to know what the maximum current I can expect individually on the Heat/Cool/Fan wires, for all other systems out there in the wild.
I also plan to revise the board with relays with a smaller package to help slim down the enclosure, so really I'm trying to figure out how low can I reasonably go.

[thm_w]

If you want ultimate compactness you can look at Nest or other IOT thermostats: https://www.ifixit.com/Teardown/Nest+Learning+Thermostat+2nd+Generation+Teardown/13818

No relays, a few FETs and a fuse instead.

Older style: https://www.ifixit.com/Teardown/Lennox+Y0349+Thermostat+Teardown/140716

[LittleRain]

Oh wow, the nest is about half the size as I thought it was.
The components used seem like total overkill, but maybe it does more than I think it does.

[thm_w]

Oh wow, the nest is about half the size as I thought it was.
The components used seem like total overkill, but maybe it does more than I think it does.

Each output appears to have at least:
- 1 diode/TVS (marked "AT")
- 2 FETs
- 1 fuse
- bunch of resistors and capacitors
- 1 diode and inductor on the top side?

The fuse is necessary if anything is accidentally connected to 120V (maybe the TVS is included in that). The two FETs are necessary if you want to switch an AC signal.
Not sure what the other stuff does, some of it will be to draw power parasitically.