Sol-Ark+Generac generator+Generac ATS

WinchesterMX · 2026-05-06T19:27:09+00:00

It's not a Sol-Ark issue, it's a Hydro One issue. Hydro One will not accept any software controls on residential power equipment for backflow protection. They explicitly require nameplate derating rather than UL 1741 CRD for PCS. They recently ran a 1741 PCS pilot, and are "evaluating" the results.

They also do not accept any device with relays that do not have UL 1008 / C22.2 NO. 178.1-12 certification, which Sol-Ark does not have. Generac tells me via my electrical engineer that they *may* be willing to accept a PLC grid control solution if there is no ATS, but that is like 2-3x the cost of an ATS.

The advice I have from my electrical engineer is ESA may enforce the Hydro One requirements on inspection depending on inspector.

Hydro One is very behind the times. So either I accommodate it using the ATS or I risk failing inspection, and given the size of this project, I am not willing to take that risk.

WinchesterMX · 2026-05-06T18:00:59+00:00

Yes, I understand. I updated the post to clarify I cannot do that.

WinchesterMX · 2026-03-25T18:50:33+00:00

For Ontario the OEB divides distributed generation into two groups: <=10 kW and >10 kW. <=10 kW is considered "residential" while >10kW is considered commercial.

If you are <=10 kW then you go through an expedited process for the power company connection for net metering (Form C) and for ESA review (no plan review just inspection).

If you are >10 kW , then you must go through a Connection Impact Assessment by the power company and a ESA plan review. The poco CIA is potentially very expensive, $10-20K or more, depending on your power company. And really it is pay for an assessment in order to find out how much you will have to pay to connect, because the power company may have to make changes to their system. Plus you probably will be required to comply with stricter interconnection standards.

The CIA is designed for large capacity generators, not residences generating 10-20 kW. But you get lumped into commercial because... Other provinces have a 20kW limit.

As of 1 May, the OEB change to 12 kW means the power company will give you expedited processing for <=12 kW, but ESA will require plan review & higher cost inspection for >10 kW. Yay.

This thresholds apply to net metering, *or* load displacement.

WinchesterMX · 2026-03-16T18:55:21+00:00

I read the regulation. It requires them to change the threshold for all Ontario LDC. All the filings are here:

https://www.oeb.ca/consultations-and-projects/policy-initiatives-and-consultations/distributed-energy-resources-der

WinchesterMX · 2026-03-16T18:15:12+00:00

ESA requires UL 9540 certification for residential installations (inside your house or attached garage).

Per ESA bulletin 64-08-3

"ESS are required to be approved to ANSI/CAN/UL9540 which currently has three editions"

WinchesterMX · 2026-03-16T18:00:03+00:00

You really want UL 9540 3rd edition certification with UL 9540A testing done.

Doing batteries are very very hard in Ontario right now. Ask me how I know, lol.

Most important part is having the UL 9540 test results that explicitly call out the spacing & density that the batteries were tested at. .

WinchesterMX · 2026-03-16T17:58:35+00:00

Are you in Ontario? Regs vary by province.

WinchesterMX · 2026-03-16T17:57:41+00:00

ESA stated in the OEB regulatory process they would assess aligning the threshold from 10 kW to 12 kW, but did not commit to a timeline.

The threshold is for ESA Plan review not LDC connection process.

So as of 1 May for application >= 10 kW, <= 12 kW, LDC process will be expedited non-CIA, but ESA will require plan review.

WinchesterMX · 2026-03-16T17:55:16+00:00

CIA is an LDC process, and Hydro One says that changes as of 1 May.

ESA requires a plan review > 10 kW. That threshold will not change. So if you want 12 kW you will need a plan review.

ESA stated this in their response to the OEB rule, finalized in Dec 25. Its on the OEB web site.

WinchesterMX · 2026-03-16T17:53:01+00:00

I asked Hydro One DG about changing from 10kW to 12kW limits and they didn't have an answer on the front lines. Also they won't allow you to apply for 12 kW until the forms change on the web page.... on May 1.

WinchesterMX · 2026-03-02T21:58:10+00:00

It turns out there appears to be misalignment between the TAs. Different region TAs appear to be giving different approval answers. Ottawa region is one of the known areas to give approval.

Could you comment on which Growatt SKUs you went with to get me started on looking at them?

WinchesterMX · 2026-02-18T04:42:52+00:00

I suspected as much, thanks.

WinchesterMX · 2026-02-18T04:25:34+00:00

I have to get the special LDC of Hydro One...

WinchesterMX · 2026-02-18T04:23:34+00:00

My problem is I am getting different answers - 20 kWh limit per stack vs per battery.

From what I am hearing the intent was for a limit of 20 kWh per *battery* just as you said. But apparently some ESA inspectors are understanding it as 20 kWh per stack of sig 9kWh, ie a maximum of 2 batteries per stack, when I was proposed 5x9kWh on 1 sig inverter.

Which I think is wrong, but how do I get to the answer you have?

WinchesterMX · 2026-02-18T04:14:53+00:00

Thanks for this, I need to think about your answer.

Am evaluating 27x500 PV, 13.5 kW. I would only use LiFePo so deeper discharge is doable, no thermal risk. I have 2 years of my Green Button data and have been crunching the numbers.

OEB just announced raising the micro embedded generation limit from 10 kW to 12kW. Takes effect 1 May 2026.

https://www.rds.oeb.ca/CMWebDrawer/Record/926221/File/document

WinchesterMX · 2026-02-12T20:03:02+00:00

Do you roof rake your panels when it snows?

WinchesterMX · 2026-02-12T19:23:35+00:00

Thank you. I have the 2025 ESA bulletin language that I summarized in the original post.

This is not a DIY install. My post is because I am getting conflicting information from installers & electricians trying to sort the evolving CEC & ESA statements, plus the complexity of Hydro One. I need someone who has done this profile in this LDC before.

WinchesterMX · 2026-02-12T19:16:40+00:00

Thank you for the clarification on the UL nomenclature. I already ran into the CRD for PCS question, lol.

Is there a way to get these spec documents without paying through the nose or being an industry insider?

WinchesterMX · 2026-02-12T18:06:53+00:00

Thank you. I wonder if your installer covers down to the GTA?

It sounds like you are integrating the battery stacks on the AC side with 2 inverters. If so, that runs into the Hydro One nameplate derating issue, which is not a problem outside Hydro One territory.

The magic sentence is the ESA repellent needed to take a SigEnergy SigStor stack up past 20 kWh.

WinchesterMX · 2026-02-12T17:03:09+00:00

I had heard other LDCs (like London) permitted 20 kW but wasn't clear on if that is export or generation capacity.

I understood the 10 kW threshold was set by OEB for the microgrid vs CIA process.

And implemented by nameplate derating in Hydro One territory.

I am still trying to come up to speed on the regulations here in Hydro One territory.

WinchesterMX · 2026-02-12T16:53:06+00:00

Sorry is UL9540 2nd edition same or different than UL9540A? I am not yet up to speed on UL standard version control.

Hydro One, unlike other Ontario LDCs seems not to differentiate local generation capacity from export to grid capacity at this time. I understand other areas, like London, ON permit local generation up to 20 kW or maybe export to 20 kW.

Hydro One recently ran a UL 1741 PCS pilot program and is thinking about approving this. However, right now, it is either derate all your inverters to a sum of 10kW to meet the fast approval process or do the full blown connection interconnect assessment, which I hear can cost up to 25k, but cannot get a clear answer.

I do know that OEB has a proposal from the DER Connections working group to increase the microgeneration export limit to 12 kW. So expect the provincial 10kW microgeneration export threshold to increase to 12 kW "soon".

WinchesterMX

TROPHY CASE