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

[August Goers]

It looks like Oncor is using the total generation facility nameplate of
PV + ESS inverter ratings, or something along those lines. That's the same
as we see in PG&E territory here in California. You might be able to use a
PCS setting to limit grid battery charging and then maybe use Aggregate
power export limit (see 5.4):

https://enphase.com/download/power-control-system-integration-enphase-energy-system-tech-brief

There are many solutions that PCS will provide if the utility
recognizes PCS as a bonafide solution.

-August




On Wed, Nov 26, 2025 at 6:57 AM scot.arey--- via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> 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
>
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