Pasadena ADU Electrical: Subpanel, Meter & PWP Service

If you're adding an ADU in Pasadena, the electrical plan is one of the first things to settle, because it touches the City permit, Pasadena Water & Power and your budget all at once. The big questions are simple: can your existing service carry a second home, should the ADU run off a subpanel or get its own PWP meter, and what does PWP need before it will energize anything? We're a licensed C-10 electrical contractor based in Pasadena, and this guide walks through those choices the way we plan them for Pasadena lots, from the old 60- and 100-amp services in Craftsman neighborhoods to newer homes. Planning an ADU or garage conversion? Request a free estimate or call 747-255-8595.

Start With Your Existing Service

Most Pasadena ADU electrical plans start at the main panel. An ADU adds a full set of loads: lighting, kitchen circuits, a range or cooktop, a water heater, heating and cooling, laundry and often an EV charger. Many older Pasadena homes still have 60- or 100-amp services that were sized long before any of that.

The way to know is a load calculation, not a guess. The electrical code (NEC Article 220) lets us add the ADU's new loads to the existing house, and in some cases use 12 months of your actual peak demand. If the numbers work, the ADU can feed from your existing service. If they don't, you're looking at a 100-amp to 200-amp service upgrade. Our load calculation guide and 100-amp vs. 200-amp comparison explain how that's decided.

Subpanel or Separate PWP Meter?

PWP's ADU requirements say a customer may have a separate electric meter for the ADU, if requested. You don't have to. There are two common setups:

• Subpanel off the main house. One PWP meter and one bill. A feeder runs from the main panel to a subpanel in the ADU. This is usually the simpler route for a family member's unit or a garage conversion.
• Separate meter for the ADU. The ADU gets its own PWP account and its own bill, which many owners want for a rental. PWP requires all meters to be at the same panel or a PWP-approved location, so this usually means a new multi-meter service panel at the house, not a second service drop to the back of the lot.

PWP also allows one underground or overhead service per property. Either way, the ADU shares the property's single service, and the meter location is PWP's call.

When the Service Needs to Grow

If the load calculation says your service is too small, the upgrade usually happens as part of the ADU project. Two PWP rules shape how far you can go:

• PWP's requirements say services larger than 200 amps at 120/240 volts will require an on-site transformer (PWP's ADU sheet notes up to 400 amps with PWP approval).
• PWP's service page says any new or upgraded single-phase service over 200 amps needs provisions for a City-owned transformer on private property.

That's why a 200-amp service is the practical target for most Pasadena ADU lots. Load management or an energy-management approach to EV charging can sometimes keep you at 200 amps. See our panel upgrade service for what the upgrade itself involves.

One rebate note: PWP's $1,000 panel upgrade rebate is for upgrading an existing panel, and PWP says new construction doesn't qualify. Whether an ADU project's main-panel upgrade fits the rules depends on the details, so confirm current terms with PWP before you count on it. Our Pasadena panel rebate guide covers the two-circuit rule.

PWP's Steps for a New Meter or Service Upgrade

PWP's Electric Service Planning page lists the process for new secondary service or a panel upgrade:

1. Schedule a meter spot with Electric Service Planning (626-744-4495 or ESP@cityofpasadena.net). A utility planner sends a panel upgrade questionnaire.
2. PWP provides an approved meter spot and a quote, if service work is needed.
3. Get the electrical permit from the City's Permit Center at 175 N. Garfield Ave.
4. Pay PWP's quote to Electric Service Planning, by check only.
5. For a new meter, open a PWP service account for each meter and get an address assignment for each meter at the Permit Center. PWP only serves legal addresses recognized by Planning.
6. For an upgrade, PWP must unlock the meter. Cutting a lock yourself brings a tampering fee starting at $300.
7. PWP inspects the panel and conduit, then Building & Safety does the final.
8. PWP lists energizing within 14 business days for small residential jobs and 21 for large ones, once all clearances are in.

PWP updated its electric service rules (Regulation 21) effective September 1, 2025, so we check the current version before every job. Our Pasadena electrical permits guide covers the City side.

Plan Details Pasadena Asks For

Pasadena's ADU submittal checklist asks the site plan to show the proposed and existing location and size of the electrical service panel and sub-panels, plus where the heat pump or AC condenser and water heater go. A few other items affect the electrical plan:

• Power lines. PWP doesn't allow building under high-voltage lines, and a structure within 10 feet of them needs a PWP encroachment application. Check this before you set the ADU footprint.
• Solar. The City notes solar PV may be required for a new ADU under the Energy Code. 911 doesn't install solar panels, but we plan the panel space and conduit so a solar contractor can tie in cleanly.
• Gas or all-electric. ADUs are exempt from Pasadena's electrification ordinance, and enforcement of that ordinance was suspended in August 2025. An all-electric ADU still needs more amps, so size for the appliances you'll actually use.
• Fees. Pasadena currently lists reduced permit fees for many ADUs on single-family lots, including those 900 square feet or smaller. Confirm with the Permit Center.

For LA-wide ADU wiring basics, see our ADU electrical wiring guide.

Frequently Asked Questions

Does a Pasadena ADU need its own electric meter?

No. PWP allows a separate ADU meter if you request it, but many ADUs run from a subpanel fed by the main house. A separate meter needs its own PWP account and address assignment.

Can I put the ADU meter at the back of the lot?

Usually not. PWP's ADU rules say all meters must be at the same panel or a PWP-approved location, and the property gets one service.

Will my ADU require a 200-amp panel upgrade?

It depends on the load calculation. Many older Pasadena homes on 60 or 100 amps need an upgrade to carry an ADU; newer 200-amp homes often don't.

Can I go bigger than 200 amps in Pasadena?

Sometimes, but PWP says single-phase services over 200 amps need on-site transformer provisions. That adds design, cost and time.

How long does PWP take to energize an ADU service?

PWP lists 14 business days for small residential jobs and 21 for large ones, after all inspections and clearances are complete.

Plan Your Pasadena ADU Electrical With a Local C-10

911 Construction & Electric Inc. is a licensed, bonded and insured C-10 electrical contractor (CA Lic. #1027421) at 1308 E Colorado Blvd Ste 141, Pasadena, CA 91106, serving Pasadena, Altadena, Glendale, Burbank, Arcadia, the San Gabriel Valley and greater Los Angeles. We handle the load calculation, PWP meter spot, City permit and ADU and new construction electrical work for homeowners across Pasadena. Request a free estimate, call 747-255-8595 or visit https://911electrics.com. 24/7 emergency service available.