Three Devils in this detail

One of the less often items discussed by solar sales folks is the issue related to interconnection ‘tests’.

Turns out that connecting to the grid ‘interconnection’ is actually regulated by the Arizona Corporation Commission (ACC). I’ll add some not-so-leisurely-reading link shortly…

The reason for this is that the residential solar power system can deliver power back to the grid. In doing so, it could negatively affect the local circuit it is connected to. It also could energize a circuit where they intend to de-energize for work/repair- a safety issue for the folks doing the good work of grid maintenance.

Residential solar power systems are considered ‘distributed generation’- they are generating power on-location of use and they are separate from the central power generation plant. They are ‘distributed’ around the grid, if you will…

All that said, here’s the three devils in this detail:

Screen A: Basically, each utility circuit (maybe up to several thousand homes) can have only so much DG capacity added safely to it. More or less- there is a max amount of solar that can go on a circuit. (Impact- there may come a time when it is too late to add rooftop solar, but probably not soon).
Screen E: The sum of all the DG capacity served by a TEP transformer cannot be more than 75% of that transformer’s rating. (Impact- same as above, there is possibility that eventually enough solar power would be installed among those served by a particular transformer that new installs would be prohibited)
Screen F: If the system is going to be a ‘single phase’ system and tap into the system at 120V- the system size has limits so it doesn’t imbalance the system. (Impact- just have to make sure the system is designed correctly, probably won’t be an issue)

So, more or less, there is a limit to how much distributed generation that can be added and every new install has to go through these ‘tests’.

Solar sales bro’s don’t talk about this much because, for now, those limits don’t really come into play very often and they’re more worried about getting an appointment to ‘sit’ with a potential customer.

Is this something to be ultra-concerned with? Probably not, but…

There is a chance that in some situations a proposed residential solar power system could be rejected because the applicable utility circuit or transformer already has distributed systems added to the limits.

Just another reason to get serious about looking into solar…

If you are interested, you can learn more about this at TEP’s website here:
https://www.tep.com/dgir-requirements/

If you, like me, love to punish yourself with tedious reading, scope out this gem- the applicable Notice of Final Rulemaking Interconnection of Distributed Generation Facilities from the ACC:
https://docket.images.azcc.gov/E000005485.pdf

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Be Good!
Curtis