Do I need a 200 amp panel upgrade for an ADU in LA?

Is there a rule that every ADU needs a 200 amp panel?

No. Electrical plans in Los Angeles are checked against the City of Los Angeles Electrical Code, which LADBS describes as based on the California Electrical Code with adopted portions of the National Electrical Code ¹. That code sizes a service by calculation (Article 220), not by the type of building you add.

LADBS's electrical plan check correction list includes an item for feeder loads that were "incorrectly calculated or omitted" ¹. In practice, the panel size on your permit is whatever the calculation for the main house plus the ADU says it must be. Contractors often quote 200 A because it is a common standard size, but the number that decides it is the calculation, so ask to see it.

How does the load calculation decide whether my 100 amp service is enough?

There are two common ways to count the load already in an existing house, and they can give different answers. A presentation from Lawrence Berkeley National Laboratory for a U.S. Department of Energy webinar explains them ²:

• Section 220.83 (existing dwelling units) estimates load from the nameplate ratings of the appliances that are installed. It tends to show a larger existing load but allows more new load.
• Section 220.87 (determining existing loads) uses metering data plus a 25% safety factor, then adds new loads at 100% of their nameplate rating.

LADBS has a modification form for adding new loads based on a one-month demand reading under Section 220.87; the reading and single-line diagram must be signed and stamped by a California registered professional Electrical Engineer ³. That is extra cost, but on a tight house it can be the difference between keeping the service and replacing it.

The same DOE-lab presentation estimates that about one in three U.S. homes has 100 A service and limited breaker slots ². If your Valley house still has its original panel, read the number on the main breaker before you talk to anyone.

Does LA still require a new ADU to be all-electric?

As of October 2026, no city ordinance requires it. Ordinance 187,714 said "All newly constructed buildings shall be all-electric buildings" for permit applications from April 1, 2023, with an exception for attached ADUs using existing gas piping systems with the main house ⁴.

After the Ninth Circuit ruled that Berkeley's similar gas ban was preempted by federal law, the City Council repealed the LA ordinance with Ordinance 188,716, effective October 13, 2025 ⁵. The repeal is retroactive and applies to any building permit for which a certificate of occupancy has not been issued ⁵. If an older article or a contractor tells you LA bans gas in new ADUs, that information is out of date.

Then why do so many new ADUs still end up all-electric?

Because the state Energy Code pushes them there. The 2025 California Energy Code took effect January 1, 2026, for permit applications submitted on or after that date ⁶. The California Energy Commission treats an ADU built new and detached from the house as a newly constructed building, and its prescriptive baseline is a heat pump water heater in all climate zones, with heat pump space conditioning ⁶. Gas is still possible through the performance approach, which uses approved compliance software ⁶.

A garage conversion is treated differently: the Commission classifies converting an existing unconditioned structure as an addition, with its own rules ⁶.

If you do choose gas, the code's electric-ready rules still reserve double-pole breakers in the main panel for future 240 V appliances ⁶, so gas does not free up as much panel space as owners expect. The appliances you pick matter too. For a new unit with one bedroom or less, the code allows a 120 V heat pump water heater in place of a 240 V one ⁶, and the DOE-lab presentation lists a 120 V heat pump water heater at about 1 kW of demand against 4.5 kW for a 240 V model ². Choices like that change the calculation.

How does an LADWP panel upgrade work?

In the City of Los Angeles your utility is LADWP, and the first step is a meter spot, not a panel purchase. LADWP says that when a contractor or homeowner plans to install a new residential service panel, "they must first request a meter spot," and that meter spotting is free ⁷.

1. Request the meter spot online. The online form covers single-family homes or ADUs with services up to 320 amps ⁷.
2. An Electric Service Representative schedules a site visit within five to fifteen business days and leaves a sketch of the panel location at the job site ⁷.
3. Keep the sketch. The LADBS inspector may ask to see it before approving the service panel ⁷.
4. For a service panel installation above a single 225 amp panel, LADWP asks for a Residential Service Planning Information Form ⁷.

On cost, one Los Angeles electrical contractor publishes a range of $3,500 to $7,500 for an LADWP panel upgrade ⁹. Treat that as a contractor's published range, not a city fee, and get your own bids.

Can the ADU have its own electric meter?

Yes, but it is an option, not a requirement. LADWP's Electric Service Requirements list, for overhead service, using the existing residential meter with no upgrade, one multiple-metering panel, up to two residential meter panels grouped together, or a commercial safety-socket or current-transformer rated meter panel ⁸.

The same manual sets the limits. A lot gets a single service lateral and service point, and unless LADWP approves otherwise, all meters and service equipment are grouped in one location on the main house ⁸. When more than one meter will be installed, the ADU needs its own legal address approved by the Los Angeles Department of Public Works ⁸. A second meter is a billing choice; it does not reduce the load the service has to carry.

What should I ask an electrician before I pay for plans?

You do not need to do the engineering yourself, but you should ask questions that make the answer checkable:

• What does my main breaker say today, and how many open breaker slots are there?
• Which method did you use for the existing house, 220.83 nameplate or 220.87 metered data ²? Can I see the calculation sheet?
• What did you assume for the ADU's water heater, heating and cooling, range, dryer and any EV charger?
• Would a 120 V heat pump water heater or a smaller unit keep us on the existing service ⁶?
• Will you request the LADWP meter spot before ordering equipment ⁷?
• Is the plan one meter or two, and if two, who is handling the separate address ⁸?

A photo of the panel and the main breaker, taken before design starts, is the kind of thing a lot check settles.

Quick answers

Sources

1. Electrical Plan Check Correction List (PC/ELEC/Corr.Lst.08, effective January 1, 2023), LADBS. Facts checked 2026-10-08
2. Low-Power Electrification, the NEC and Building Energy Codes (DOE Codes Webinar, 2024-04-18), Lawrence Berkeley National Laboratory. Facts checked 2026-10-08
3. Request for Modification: 30 Day Demand (PC-ELEC.Mod 7), LADBS. Facts checked 2026-10-08
4. Ordinance No. 187714 (all-electric buildings), City of Los Angeles. Facts checked 2026-10-08
5. Ordinance No. 188716 (repealing Ordinance No. 187,714), City of Los Angeles, Office of the City Clerk. Facts checked 2026-10-08
6. 2025 Energy Code: Single-family Accessory Dwelling Units (ADU), California Energy Commission. Facts checked 2026-10-08
7. Request a Meter Spot for Single Family Residential Home or ADU up to 320 Amps, LADWP. Facts checked 2026-10-08
8. Electric Service Requirements, 2024 Edition, Section M: Accessory Dwelling Unit (ADU), LADWP. Facts checked 2026-10-08
9. DWP Electrical Panel Upgrade (contractor's published price range), LA Pro Electrical (contractor). Facts checked 2026-10-08

Greenlight is not a contractor, architect or engineer, and this is not legal advice. Rules change; every fact here shows the date we last checked it.