I came across this today - http://mistbox.com/ a mist system for an AC box which claims to reduce energy by up 30%. I figure the same could be built for very few dollars and could use my current ecobee themostat information to determine when my AC is running by looking at the ‘operation’ value reported by the ecobee API into HA. I am looking for something that could interface with HA to act as a relay to drive a solenoid. I have a Pi 2b and 3 along with a spare Sonoff switch.
EDIT: Just came across the Sonoff SV. Thinking this may do the job.