topic Re: Advanced Nest programming (for solar and multiple HVAC units) in Home Automation

Advanced Nest programming (for solar and multiple HVAC units)

Austintatious — Fri, 01 Sep 2023 13:17:32 GMT

Hello all. I have an oddball situation I need help with.

I have 4 HVAC units in my home (yea I know).... I also just had a large solar array installed on the home... At peak sunlight hours the array is capable of running 2 of the HVAC units while still slightly running the meter backwards.

What I would like to do is be able to set temps in the home on the app, but with a constraint that only 1 HVAC unit is allowed to be cooling or heating at a time. This will keep me from drawing power from the grid (costing me money)

Additionally I want this limitation to only apply during a certain time frame. From about 11 am until 6 PM.... (this will change in summer vs winter)

Ultimately I would want to set up some sort of IFTTT scheme to actually look at solar power available and have a load shedding priority to keep from drawing from the grid when solar is available.

IF anyone has any advice or ideas, I am all ears!

Re: Advanced Nest programming (for solar and multiple HVAC units)

00StEVEN — Fri, 08 Sep 2023 02:20:59 GMT

As a low tech solution, you could use the Nest schedules to achieve what you're looking for. You could have each HVAC unit set to the desired temperature for 30 minutes, and then set to an offset temperature for the next 30 minutes, with a start time for each unit offset for 15 minutes. For example, HVAC #1 set to 70F from 11am-11:30am, then 80F from 11:30am-12pm; then HVAC #2 at 70F from 11:15am-11:45am, then 80F from 11:45am-12:15pm; then HVAC #3 at 70F from 11:30am-12pm, etc etc. That way you are more than likely to only have 2 units running at any time, and the start up loads for the units are spread out. Tinkering with this philosophy may be required. You might want the units to run for longer to decrease cycling, if that matters.

Re: Advanced Nest programming (for solar and multiple HVAC units)

mikepole — Thu, 17 Jul 2025 05:46:48 GMT

That's a great idea

Re: Advanced Nest programming (for solar and multiple HVAC units)

mikepole — Thu, 31 Jul 2025 05:32:43 GMT

You can achieve this using smart thermostats (like Ecobee or Nest) combined with a home automation platform like Home Assistant or SmartThings. Set up rules to allow only one HVAC unit to run between 11 AM and 6 PM, based on your solar output. Use an energy monitor (like Sense or Emporia) to track solar production and trigger HVAC priority. I’ve seen similar setups recommended by a solar company in Lahore, and it’s a great way to reduce grid usage and save money.