Santa Clarita, CA · April – September 2025 · Southern California Edison / City of Santa Clarita

Santa Clarita: the second unit got a service of its own.

Six modules on a new accessory dwelling. The design changed twice, and both times because of what was feeding it.

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

A new accessory dwelling can share the main house's electric service or be given its own, and that single decision governs the solar design: what the array connects to, where the arithmetic is done, and which address the interconnection is filed under. On this Santa Clarita project the unit was first drawn against a 125 A sub panel and then changed to a dedicated 200 A service of its own, sited beside the main house panel, with a 200 A sub panel on the unit itself. Cali Energy redrew the six-module array around it.

At a glance

Property

New accessory dwelling

Array

Six Canadian Solar 400 W modules

Inverters

One Enphase IQ7A per module

Roof

Metal, re-covered with shingle

Service

Own 200 A main, 200 A sub panel on the unit

Utility / AHJ

Southern California Edison / Santa Clarita

The story

Six modules on a new second unit. As small as solar projects get, and the design still changed twice before anything was built — both times because of the service rather than the roof.

The first version assumed the ordinary arrangement: the unit hangs off the property's existing supply through a 125 A sub panel, and the array connects there.

The second version is what actually happened. The unit was given a service of its own — a dedicated 200 A main panel sited next to the main house's panel, with a 200 A sub panel at the unit itself.

That is a different building, electrically, and it is worth understanding why it changes so much for a six-panel array.

A shared service makes the second unit part of the main house as far as the utility is concerned: one meter, one account, one premise, and anything connected to it is filed under the main address. A dedicated service makes it its own premise, with its own meter, its own account and its own interconnection.

For the solar that decides three things at once. What the array backfeeds — the unit's own panel rather than the house's. Where the 120 percent arithmetic is done — on the panel it joins, which at 200 A has room a 125 A sub panel would not. And which address the interconnection application belongs under, which is the part that quietly costs weeks when it is got wrong.

There is a sequencing consequence too, and it was visible here: the project waited on the meter spot. Until the utility has marked where the new service and meter go, the unit has no service to connect to, and solar filed against it has nothing to attach to.

The roof had its own wrinkle: metal, re-covered with shingle, which changes what the array fixes into and has to be settled before attachments are ordered rather than after.

One more thing about the end of a project like this, because owners ask it almost word for word: the array cannot be switched on when the crew leaves. Permission to operate comes from the utility, and until it is issued the system stays off. Here the interconnection application came back with corrections and a ten-day clock on them; they were answered the same day.

What an owner should take from this: if a second unit is going in and solar is anywhere in the plan, the metering question is the first one to answer and it is not a solar question at all. One meter or two decides the panel the array joins, the address the paperwork carries and roughly how long the whole thing takes.

Permission to operate was granted at the start of September, with the monitoring already live, and the second unit has been generating on its own service since.

Cali Energy designed, permitted and installed this accessory dwelling array in Santa Clarita.

How it ran

Four and a half months from the first drawing to permission to operate, and the decision that shaped all of it was how the second unit would be metered.

What we did

• Drew the array against the sub panel first, then redrew it when the service changed.
• Waited on the meter spot rather than filing against a service that did not exist.
• Settled the roof construction before attachments were ordered.
• Kept the interconnection filed against the address that would hold the meter.
• Answered the utility's ten-day correction notice the day it arrived.

System specifications

Is your project like this one?

• You are building an accessory dwelling and want solar on it.
• Nobody has told you whether the new unit gets its own meter.
• Your second unit is drawn off a sub panel and you are not sure it should be.
• Your roof is metal and something is going on top of it.

Cali Energy in Santa Clarita

Frequently asked questions

Should an ADU have its own electric service?

It can go either way, and the choice is made at the meter spot stage rather than when solar is designed. A dedicated service makes the unit its own premise with its own meter and account; a shared one makes it part of the main house as far as the utility is concerned.

How does the metering decision change the solar design?

It decides what the array backfeeds, where the 120 percent arithmetic is done, and which address the interconnection is filed under. A dedicated 200 A panel has headroom a 125 A sub panel does not, and the address on the application is what determines whether it is processed or closed.

Why does a new unit wait on a meter spot?

Because until the utility marks where the service and meter physically go, the unit has no service. Solar filed against a premise with no service has nothing to connect to, and the application does not queue — it gets closed.

Can solar go on a metal roof?

Yes, and the attachment depends on what the roof actually is. On this project the metal had been re-covered with shingle, which changes what the mounts fix into, and that has to be settled before hardware is ordered rather than discovered on the day.

Does Cali Energy install solar on accessory dwellings in Santa Clarita?

Yes. Santa Clarita permits through its own Building & Safety Division and interconnects through Southern California Edison. Second units are going up steadily on these lots, and the first thing settled on them is how the unit will be metered.

What this would look like on your roof

Related

• The ADU was on the main house meter West Adams, Los Angeles · which address the interconnection belongs under Solar
• The final passed and the project was not done Santa Clarita · six days to the signature, three weeks to the handover Solar
• The unit had no address, so the application went in under the main house Granada Hills, CA · 1.99 kW on an ADU · 108 days, almost all of it records Solar
• Twenty-one microinverters became one inverter Santa Clarita · 7.56 kW · the roof chooses the architecture Solar

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