[RE-wrenches] 2KW PCS import/export limit on a 25KW transformer; Oncor in Texas

[scot.arey at solarcentex.com]

In my 13 years installing solar in Texas, I've never had a utility come back and say "you must set a PCS limit of 2KW through this 25KW transformer or you can pay to upgrade the transformer."

System is 12KW of solar (9KW AC equiv.) and 6x Enphase 5P batteries (23KW AC) so total of 32KW of potential power export if the batteries were grid-exporting at same time of peak solar production. I can see the batteries charging at 23KW if charging from grid but of course solar can never be a load.  And exporting battery power simply not a financially smart option.

So the only answer I can come up with is this transformer is serving more than this home and seems undersized by utility if it's serving multiple homes with 200-amp services. Few words from Oncor is that this is the issue.

I alerted Oncor to the Power Control System capabilities to limit power export and they are insistent that 2KW is all they can take (they never said if this a import or export limit). I asked if this was a grid-tied system only with no ESS, would it have come back with the same 9KW (AC) limit? I think they are tripping over the combined connected capacity of solar + ESS.

Anybody else in Texas running into this recently? I told Oncor I'd be perfectly fine with 9KW export capability (the solar) and limit grid-charging to this power, too.

This isn't Hawaii...so I'm super surprised and about to lose a lot of money.

Howard "Scot" Arey
Owner, Solar CenTex

NABCEP PV Installation Professional
TECL 29755
254-300-1228
[cid:3833d2ce-5501-4b5c-9d22-f2071037571a]

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