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Author Topic: Solar Panel Installation Question re: Air Conditioning  (Read 86 times)

AZRedhawk44

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Solar Panel Installation Question re: Air Conditioning
« on: August 03, 2022, 06:49:56 PM »

I'm considering a solar panel installation on my house here in Arizona.

Last month's bill had me using 3000 kilowatt-hours.  Of that, 876 were on-peak and 2200 were off-peak.  On-peak power costs about 25 cents per kwh.  Off-peak is about 7.5 cents.

If I put a 4000 watt array on my roof, flat with no tracking axis hardware, I can generally count on about 6.5 hours of power production.  That comes out to around 780 kilowatt-hours per month.  A significant portion of my 876 on-peak kwh.

But here's the rub:  I don't get a 1:1 trade with SRP for excess energy I add to the grid versus what I pull from it.

Now we get to the architecture question.

My house has two air conditioners.  One controls the front half of the house, the other controls the back half.  Each is a 30 amp circuit, probably chewing 4000-5000 watts a piece when running.  The thermostats are set to identical temperatures and they both tend to start running within seconds of each other, and shut off around the same time too.  So they run for 5-10 minutes, then sit idle for 20-30 minutes.

If I deploy a 4000 watt solar array in this environment where 8000 watts of demand hits for 10 minutes then disappears for 20 minutes, I'm going to be asking SRP for 4000 watts from their grid 1/3 of the time, then giving them 4000 watts 2/3 of the time.

I want to set up a system so that if the front AC unit is running, the back unit is prohibited from running.  If the back unit is running, the front is prohibited from running.  That would turn into a system where my solar array powers (at least most) of my first AC unit for 10 minutes of run time, then the second unit for the next 10 minutes, then I'm dumping excess into the SRP grid if no AC unit wants to run and the remaining household power usage is under 4000 watts.

Anyone know of any kind of smart thermostat available that rations runtime between multiple air conditioners like I want?
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AZRedhawk44

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Re: Solar Panel Installation Question re: Air Conditioning
« Reply #1 on: August 04, 2022, 03:41:00 PM »

Update on this.

The feature I'm looking for is called Demand Automation, and it's a feature installed at the circuit breaker level of a house rather than in a thermostat.

Here's one manufacturer of such a system.

https://www.brayden.com/

The net result is a staggering of big consumers in order to achieve a targeted max threshold of consumption.  Once one big consumer finishes its job (i.e. air conditioner), another consumer is free to run (such as an electric water heater).  You only put devices onto the demand automation system that won't be adversely affected by a breaker-level cut in power.  You wouldn't put your clothes dryer or your circuit you use for welding in the garage on this thing, but water heaters and hvac are good candidates.

Evidently my power company, SRP, gives different electrical rates for customers that go to a peak demand model and use demand automation to control that.  I just got a quote from a consultant and demand automation can cost less to install and result in greater savings than adding a significant solar array to my house.

I have a quote for a 4000 watt solar system along with demand automation.  It should make a huge crater in my summer electric bills, and turn my winter bills mostly into connection fees and taxes.

It seems like a device like one of these should be a standard installation device on any off-grid solar installation.
"But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist."
--Lysander Spooner

I reject your authoritah!