Coordination of two thermostats' cool cycles

Disclosure: I don't own a Hubitat device and only superficially understand it's/their capabilities from half a morning's webbing,

I don't know how to succinctly ask my question, so bear with me...

  • We have two A/C units, independent of one another, each with their own Nest thermostat
  • We have solar panels
  • When both A/C units run concurrently, the demand exceeds solar generation - necessitating buying Kws off the grid

Would like to have a rule wherein if one unit is cooling (thermostat activating Yellow wire), the other unit is precluded from cooling. When the first unit completes its cooling cycle, the second unit can start. Hopefully, lessening our Kws buys.

Can Hubitat devices manage that? If so, can the base model do it?; or will a more capable device be needed?

Appreciate time and attention.

Hubitat would be able to create a rule like this. The big question is what type of Nest thermostat do you have? If it is the learning version, you'll need to use a community app to bring it into Hubitat. If it is the entry model with Matter, you could use Matter to bring it into Hubitat.

As for as which version of Hubitat, if you plan to use Matter, I'd recommend getting the C-8 Pro as it has a little bit more headroom. If you are using the community app, the regular C8 or even the C7 would work.

Yes that could be done with rule machine but it could also cause a unit(s) to work harder trying to keep up with the heat load.

The Hubitat hub can do this assuming the Nest can be controlled. I'm not familiar with the Nest, I know my Honeywell's can.

My question is: Can your A/C keep up if it is not allowed to run the amount of time required to satisfy the thermostat? Ideally each will run at 50%. However I guess when one goes on it will stay on until the thermostat is satisfied, while the other section of the home gets much warmer. Then the 1st thermostat will shut off the A/C and the 2nd will come on until it is satisfied. All resulting in the 1st section of the home heating up.
The result is a lot of variation in temperature. And if 1st goes on and its so hot it cannot meet the thermostat setting, the 2nd will never come on.

If you were to consider Hubitat, you could create "rules" that would at some point allow both A/C to be running at the same time. Actually you could make pretty much any rule you can think of.

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Easy to do. But it could be unreliable with a Nest thermostat. I'd recommend replacing them with good locally-controlled z-wave/zigbee thermostats. When used in conjunction with Home Assistant, Hubitat can also control ecobee thermostats locally.

Thank you all for your replies.

As to the concerns of the A/C units keeping up with extended periods of not running...I don't know. Perhaps I'll do some crude stat gathering as to percent of time that the units are on. The house is a one story with fairly open floor plan...except for a couple of bedrooms, the temp is fairly consistent through-out (probably as a result of units running when the need to :grinning:)

The intent would be to have the rule in effect only during solar generating hours (I know, the hottest part of the day). When we're buying off the grid, regardless, they can overlap running as needed.

Thanks again. Lots to consider.