I would like my A/C to self turn on at 8pm, that is before I get home and have the ability to cut off power automatically. I have Sonoff basic devices doing this with my lawn lights, pool, etc. I have a 1 Channel Inching /Self-Locking WiFi Wireless Switch 5V 12V that's been sitting here unused:
I connected it to 1 zone of my sprinkler system and it worked as expected - when the sprinkler controller turned on that zone I could turn on/off the Sonoff WIFI switch which then turned on/off that zone but for so long, then off. I thought it's summer, turn the HVAC selector to AC, find the power line, cut it, insert them in this low voltage Sonoff, and I can turn on/off AC on my phone or just use a set timer. The thermostat is a Honeywell RTH110B here is installation manual. Sonoff device is powered by cellphone charger or 12vc dc connectors.