El Sereno, CA · June – July 2021 · LADWP / LADBS

El Sereno: what an installer certifies and what it does not.

Twelve modules and an ordinary roof. The question that took the time was about equipment that was already on the wall.

Written by the Cali Energy project team · California contractor license 1032379 · Updated September 2026

Solar is usually connected into electrical equipment that is already there, and on older housing that equipment has often been altered by somebody nobody at the project can name. Two separate questions follow. Whether a solar breaker can physically and lawfully land in that panel is one. Whether the installer will stand behind the wiring already inside it is the other, and the answer to that is no. On this 4.44 kW El Sereno project in Los Angeles, Cali Energy settled both questions with the cover off and in person before the crew was scheduled.

At a glance

System

4.44 kW

Array

12 modules, 370 W each

Roof

Composition shingle

Main panel

No upgrade required

Settled before scheduling

An existing sub-panel, assessed with the cover off

Utility / AHJ

LADWP / LADBS

The story

Twelve modules at three hundred and seventy watts, a composition shingle roof, no main panel upgrade. Intake was on the fourth of June and the crew was offered for the tenth.

The crew went out on the twenty-first.

Ten days after intake a question came back about the sub-panel. The owner had had somebody work on it, and nobody on the project could say what had been changed or by whom. The question put to us was simple: is a new sub-panel still needed, or can the solar land in the existing one?

There are two questions inside that, and they get confused constantly.

The first is whether a solar breaker can go into that panel — whether the busbar and the breaker sizing work, whether there is a space, whether the result complies. That is an ordinary design question with an ordinary answer.

The second is whether the company landing that breaker is now standing behind everything else inside the enclosure: the breakers somebody else fitted, the conductors somebody else landed, the workmanship nobody documented. That answer is no, and it needs to be said out loud before the crew is scheduled rather than afterwards.

So the position we gave was in two parts. We can fit the solar breaker into the existing sub-panel. We are not taking responsibility for the breakers and the wiring that were already in it. And if what is wanted is an actual assessment of that panel rather than a yes, we need a photograph with the cover off, because nothing useful can be said about a panel from the outside of a closed door.

The photograph came two days later. The panel was looked at properly and it was sound, the install was set for the following Monday, and the array went up on the twenty-first.

The inspection request went in on the twenty-third, the final was set for that Saturday, and it passed. Permission to operate came in the middle of July.

One detail about switch-on that catches people out. A system here is left switched off until permission to operate arrives — it is not a formality, and running before then is exporting onto a network that has not agreed to take it. When the permission does arrive there is an order to turning it on: the solar breaker first, then the inverter. Doing it the other way round is not dangerous, but it is a good way to have an inverter sit there reporting a fault while somebody assumes the system is broken.

And the wider point, which applies to any house that has had electrical work done over the years. Ask your installer directly what they are certifying. There is a real difference between 'we can connect to this' and 'this is sound', and the difference is worth eleven days.

Cali Energy designed and installed this array in El Sereno, Los Angeles.

How it ran

Eleven days between the date first offered and the date the crew went out, all of it spent on equipment that was already on the wall.

What we did

• Separated the design question from the responsibility question and answered both.
• Refused to assess a panel from a photograph of a closed cover.
• Assessed the opened sub-panel before scheduling the crew.
• Installed twelve modules and carried the project to a passed final inspection.
• Gave the switch-on sequence at permission to operate.

System specifications

Is your project like this one?

• Your panel or sub-panel has been worked on by somebody you cannot name.
• An installer has said they can connect but will not warrant what is already there.
• You are not sure whether you need a new sub-panel for solar.
• You have permission to operate and nobody has told you how to switch on.

Cali Energy in El Sereno

Frequently asked questions

Can solar connect to an existing sub-panel?

Often yes. It depends on the busbar rating, the main breaker, the backfeed breaker size and whether there is a space for it — an ordinary design question. What it does not depend on is who installed the panel, which is a separate question about responsibility rather than about whether the connection complies.

Is my installer responsible for wiring they did not install?

No, and it is better to have that stated before the crew is scheduled. An installer landing a solar breaker in an existing enclosure is certifying the solar circuit, not the breakers and conductors somebody else fitted years earlier. Ask directly what is being certified; the difference between 'we can connect to this' and 'this is sound' is a real one.

Can a panel be assessed from photographs?

Not from a photograph of a closed cover. The condition of an enclosure is about what is inside it — how the conductors are landed, what the breakers are, whether the workmanship holds up. On this El Sereno project the assessment waited until a photograph with the cover off was available, which cost two days and settled the question properly.

How do I turn my solar system on after permission to operate?

The solar breaker first, then the inverter. Until permission to operate arrives the system stays off — running before then means exporting onto a network that has not agreed to accept it. Switching on in the wrong order is not dangerous, but it can leave an inverter reporting a fault and an owner assuming something is broken.

Does Cali Energy install solar in El Sereno, Los Angeles?

Yes. El Sereno is inside city limits, so projects here are permitted through LADBS and interconnected through LADWP. The housing is older and smaller than average for the city, and the service equipment has often been added to over the years, which is why what is already on the wall gets looked at before a date is set.

What this would look like on your roof

Related

• Derating the main breaker was the cheap answer. It was not the one used Burbank, CA · 9.72 kW · a solar-ready 400 A panel instead of a derate Solar
• The panel came out. What went back has a bigger busbar Granada Hills, CA · 6.00 kW DC · 225 A busbar, 70 A of headroom left Solar
• Solar inside a historic overlay zone Mid-City, Los Angeles · 18 modules · where the panels may go is decided first Solar
• What the numbered progress updates mean Palms, Los Angeles · 11.6 kW · the notice that needs your signature Solar

This timeline reflects this property and this permitting path. Updated September 2026.