Research study
Does an ADU need a service upgrade?
The honest answer is that a web page cannot tell you. What a page can do is name the four inputs that decide it — and flag the one that has quietly inverted since 2023.
Written by HyreADU Research Desk Primary-source research and data analysis
Audited by HyreADU Research Desk Code citation and retrieval-date audit
The finding
There is no square-footage rule, no bedroom rule and no “an ADU needs 100 amps” rule. The answer comes from a load calculation. A licensed C-10 electrical contractor or an electrical engineer computes the calculated load of the whole property, existing dwelling plus new unit, against the California Electrical Code (Title 24, Part 3 of the California Building Standards Code) and compares it to the rating of the existing service.
If the calculated load exceeds what the service can carry, the service is upgraded. If it does not, it is not. Nobody should size a service from a website.
The finding worth publishing is that gas has become the expensive choice in panel terms, not the cheap one. Since the 2022 Energy Code took effect on 1 January 2023, a newly constructed single-family building that installs gas or propane space heating, water heating, cooking or clothes drying must be made electric-ready for each of them: a dedicated 240-volt circuit and a reserved double-pole breaker space per appliance, adding up to 140 amps of reserved circuits if all four end uses go gas. Whether that mandate applies to your ADU turns on a classification, not on a design choice. A detached, newly built unit is a newly constructed building and carries the mandate; a conversion of existing space, attached or detached, is an addition and does not.
Metering is a third question, and an unresolved one: state law bars a permitting agency from requiring a separate utility connection for a by-right ADU, while PG&E’s filed tariff says residential units shall be individually metered. Both stand as retrieved. This page explains what the code requires.
It is not legal or engineering advice, and it is not instruction for performing electrical work.
Read this first
- Nothing on this page is instruction for performing electrical work, and none should be inferred
Electrical service, panel, meter and branch-circuit work on a dwelling in California is the work of a licensed C-10 electrical contractor, under permit and inspection.
This page describes what the code requires so that you can brief a professional and read their proposal.
It does not describe how to do anything, and a homeowner who treats it as a how-to has misread it.
The consequences of getting service work wrong — an unbonded neutral, an undersized service conductor, a back-fed panel — are fires and electrocutions, and they are not visible after the drywall goes up.
- We do not publish the California Electrical Code text, because we could not retrieve it
The California Electrical Code is Title 24, Part 3 of the California Building Standards Code. We confirmed its edition and effective dates from the Building Standards Commission’s own codes page, but the code text itself sits behind a publisher and we did not retrieve it.
So this page cites the load calculation by name and by code part; it does not quote article or section text, and it publishes no demand factors.
Anyone quoting those to you should be able to show you the article number.
- A load calculation is property-specific and cannot be generalised
Two identical ADUs on two identical lots can produce different answers because the existing houses differ — an older 100-amp service with a gas range and gas heat, against a 200-amp service already carrying a heat pump and an EV charger.
The calculation is about the whole property, not about the ADU. Anyone who quotes you a service size before seeing your panel and your existing loads is guessing.
- The Energy Code and the Electrical Code are different books doing different jobs
Title 24, Part 6 (the Energy Code) decides what must be reserved and readied. Title 24, Part 3 (the Electrical Code) decides what may be connected and how. A design can satisfy one and fail the other. Both are enforced by the same building department, usually by different plan checkers.
The four things that decide the answer
Strip out the folklore and the question “does my ADU need a service upgrade?” resolves into four inputs, in this order.
One: the rating and condition of the existing service. Not the main breaker sticker — the service equipment, the conductors and the utility’s point of delivery. A 100-amp service is the common constraint on California housing stock built before the 1980s, and it is the single most frequent reason an ADU budget moves.
Two: the existing calculated load of the house. A house that has already absorbed a heat pump, an induction range and an EV charger has spent capacity an ADU now needs. Electrification of the primary dwelling and construction of an ADU compete for the same amperage.
Three: the ADU’s own load, which is largely a fuel choice. An all-electric unit carries a heat pump, a heat-pump water heater and an induction cooktop as real connected load.
A gas unit carries less connected load — but, if it is a newly constructed building, it must still reserve the circuits and breaker spaces the Energy Code demands for the future electric replacements. That is the inversion this page exists to point at.
Four: whether the unit is separately metered. A separate service to the ADU changes the calculation entirely, because it is then a separate service with its own calculated load rather than an addition to the house’s. Whether it can be required, or refused, is the legal question dealt with below.
HyreADU analysis: the reason “does an ADU need a panel upgrade?” has no published answer is that inputs one and two are properties of the existing house and are unobservable from the street.
Every general figure you will find on the internet is answering input three only, and input three is the least binding of the four.
What the Energy Code makes you reserve when you choose gas
Mandatory measures under Energy Code sections 150.0(n) and 150.0(t)–(v), as set out in the California Energy Commission’s 2022 Single-Family Residential Compliance Manual, chapter 10. These apply to a newly constructed single-family building — which includes a newly built detached ADU — and they apply per gas appliance installed.
| Gas or propane appliance installed | Circuit that must be installed | Panel space that must be reserved | Other required provision |
|---|---|---|---|
| Cooktop or range | 240 V branch circuit, minimum 50 amps, within 3 feet of the cooktop, no obstructions, dedicated to the future electric replacement and not usable for other appliances. A receptacle is not required, but unused circuits “must have a blank cover identified as ‘240V ready’.” | “Dedicated space in the main service panel for a double pole breaker,” identified as “Future 240V Use.” Breakers need not be installed at construction. | Applies when installing a gas range; “not required for gas ovens when installed as a separate appliance.” |
| Furnace (space heating) | 240 V branch circuit, minimum 30 amps, within 3 feet of the furnace, no obstructions, dedicated to future electric replacement equipment. | Dedicated double-pole breaker space, identified as “Future 240V Use.” | “If gas equipment other than a furnace is installed these electric ready requirements do not apply.” |
| Water heater — designated heat-pump space within 3 feet | A dedicated 125 V, 20 amp receptacle within 3 feet of the water heater, wired on a “120/240V, three conductor, minimum 10 AWG branch circuit”, with the unused conductor ends labeled “spare” and electrically isolated. | A reserved single pole breaker space next to the branch circuit breaker, labeled “Future 240V Use.” | A designated space 2.5 ft wide × 2.5 ft deep × 7 ft tall must be reserved for a future heat-pump water heater, plus a condensate drain “no higher than 2 inches above the base of the tank.” |
| Water heater — designated heat-pump space more than 3 feet away | 240 V branch circuit rated at a minimum of 30 amps, no obstructions. | Dedicated main-panel space for a future double-pole breaker, identified as “Future 240V Use.” | Exposed, readily accessible hot and cold water supply piping must be run to the designated location; hot water from the gas heater “must be routed to the designated HPWH location first before serving any of the hot water fixtures.” |
| Clothes dryer (where gas piping to serve one is installed) | 240 V branch circuit, minimum 30 amps, within 3 feet of and accessible to the dryer location, dedicated to future electric replacement equipment, blank cover identified as “240V ready”. | Dedicated double-pole breaker space, identified as “Future 240V Use.” | — |
| Outdoor grills, barbecue pits, fireplaces, stand-alone ovens | None required. | None required. | “Any gas appliances not listed … are not required to meet the mandatory electric ready requirements.” |
Quoted from the CEC 2022 Single-Family Residential Compliance Manual (CEC-400-2022-006, May 2022), chapter 10, “Electric Ready Requirements”. The 2022 Energy Code took effect 1 January 2023; the 2025 Energy Code applies to permit applications submitted on or after 1 January 2026 and its provisions were not retrieved for this edition.
HyreADU analysis. The manual is explicit that these are mandatory measures with no trade-off: “[t]here are no performance or prescriptive electric ready requirements for single family buildings”, meaning you cannot model your way out of them.
It is equally explicit that “[t]hese requirements are for newly constructed buildings and are not applicable to additions or alterations,” and that they are “not applicable when electric equipment is installed.” An all-electric ADU has no electric-ready obligation at all, because it is already the end state the mandate is reserving space for.
Addition or newly constructed building? The test that decides everything
The Energy Commission publishes the classification test for ADUs directly. It decides whether the electric-ready mandate bites, and it is not a matter of judgment — it turns on two facts: attached or detached, and converted or newly built.
| The ADU | Energy Code classification | Electric-ready mandate applies? | CEC wording |
|---|---|---|---|
| Detached, newly constructed structure | Newly constructed building | Yes, for each gas end use installed | “If the ADU shares no common walls with the existing dwelling unit (detached) and is a new structure, this is a newly constructed residential building.” |
| Newly constructed, attached to the existing home by a breezeway or covered walkway | Newly constructed building | Yes | Listed by the CEC under “Newly Constructed Building: Newly constructed ADU attached to existing home by breezeway, or covered walkway.” |
| Conversion of existing unconditioned space, detached (e.g. a detached garage) | Addition | No | “Addition: Converting existing unconditioned space, detached from existing home. Walls may qualify as ‘existing wall with siding.’” |
| Conversion of existing unconditioned space, attached (e.g. an attached garage) | Addition | No | “Addition: Converting existing unconditioned space, attached to existing home.” |
| Newly constructed and attached to the existing home | Addition | No | “Addition: Newly constructed, attached to existing home. One or more walls may qualify as wall extensions.” |
| Newly constructed on top of, or beside, an existing detached garage | Addition | No | “Addition: Newly constructed ADU on top of existing detached garage or side-by-side with existing detached garage.” |
| Junior ADU inside an existing single-family residence | Addition | No | A JADU is “contained entirely within an existing single-family building.” The 2022 code separately excepts JADUs classified as additions from the whole-dwelling mechanical ventilation requirement. |
Compiled by the HyreADU Research Desk from section 9.3.5 and Figure 9-2 of the CEC 2022 Single-Family Residential Compliance Manual (May 2022), retrieved 2026-09-05. The classification column and the CEC wording are the manual’s; the electric-ready column is the desk applying the manual’s own statement that the mandate does not reach additions or alterations.
The manual adds a caution worth repeating: “Although the Energy Code that applies to the ADU may be the same as an addition, this may not be the same for other Parts of Title 24. Check with your local building department to confirm applicable requirements.” The Energy Code classification does not travel to the Electrical Code, the Residential Code or the Plumbing Code.
How to get the answer, in order
Every step here is something you commission or ask for. None of it is something you do to a panel.
- 1 Photograph the existing service equipment and read the label — do not open anything
The main service panel’s label carries a bus rating and the main breaker carries an amp rating, both readable from outside the enclosure with the dead front closed.
That, plus the meter, plus a photograph of the service drop or lateral, is enough for a contractor to start.
Do not remove a dead front, and do not open the meter enclosure. The conductors upstream of the main breaker are live at all times and cannot be switched off from inside the house.
- 2 Commission a load calculation from a licensed C-10 contractor or an electrical engineer
This is the deliverable that answers the question. It is performed against the California Electrical Code — Title 24, Part 3 — on the whole property, and it produces either “the existing service is adequate” or a required service size.
Ask for it in writing, with the code edition and the method identified. Verify the contractor’s license on the Contractors State License Board’s public register before you engage them.
- 3 Settle the fuel question before the calculation, not after
Whether the ADU is all-electric or carries gas appliances changes both the connected load and, if the unit is a newly constructed building, the reserved circuits and breaker spaces the Energy Code demands.
Deciding fuel after the panel is specified is how projects acquire a second panel. Our reach-code study covers the jurisdictions where the choice may already have been made for you.
- 4 Ask the serving utility, in writing, which rule governs metering at your address
Ask for the rule number and its effective date, not a verbal answer.
If the utility asserts a separate meter is required, ask how it reads that against Government Code section 66311.5(d), which bars a permitting agency — a definition that includes utilities — from requiring a separate connection for a by-right ADU.
The written exchange is the document that matters later. See our utility connection study.
- 5 If the ADU already exists without permits, read Government Code section 66311.7 before you disclose anything
That section bars denial of a permit for an unpermitted ADU built before 1 January 2020 except where “correcting the violation is necessary to comply with the standards specified in Section 17920.3 of the Health and Safety Code,” and provides that inspectors “shall not penalize an applicant.” Section 17920.3(d) makes substandard “all wiring, except that which conformed with all applicable laws in effect at the time of installation if it is currently in good and safe condition and working properly.” Existing wiring that is genuinely unsafe will have to be corrected, and should be.
- 6 Budget the upgrade separately from the build, because it is the utility’s schedule, not yours
A service upgrade often involves the utility as well as the contractor, and the utility’s work sits on the utility’s program.
Where PG&E is the provider, Electric Rule 16 governs the service extension and states that PG&E “will be responsible for planning, designing, and engineering its Service Extensions using PG&E’s standards.” That is not a schedule a general contractor controls.
The separate-meter question, and why it is unresolved
The statute is clear about what a permitting agency may require
For an ADU or JADU within the by-right categories in Government Code section 66323, section 66311.5(d) bars a local agency, special district or water corporation from requiring the applicant “to install a new or separate utility connection directly between the unit and the utility or impose a related connection fee,” unless the unit was built with a new single-family dwelling or is being separately conveyed.
That reaches utilities directly, because section 66313(k) defines a permitting agency to include “utilities, and special districts”. Section 66311.5(b) adds that an ADU “shall not be considered … a new residential use for purposes of calculating connection fees or capacity charges.”
The filed tariff we could read says something else
PG&E Electric Rule 16, “Service Extensions”, at B.3.a: “For revenue billing, electric service shall be individually metered to every residential unit in a residential building or group of buildings or other development with multiple tenants such as, but not limited to, apartment buildings, mobile home parks, etc., except as may be specified in Rule 18 and applicable rate schedules.” At C.2: PG&E “will not normally provide more than one Service Extension … for any one building or group of buildings, for a single enterprise on a single Premises,” subject to listed exceptions.
The version we read is Revised Cal. P.U.C. Sheet No. 59584-E, filed under Advice 7572-E, submitted 17 April 2025 and effective 17 May 2025. It is current.
We report the tension and stop
HyreADU analysis. There is a real question here about how a filed CPUC tariff and a Government Code provision interact on a single-family premises with a by-right ADU.
We found no CPUC decision, HCD guidance or published legal analysis resolving it that we could retrieve on this date, and hcd.ca.gov was returning HTTP 403 throughout. So we do not resolve it.
What we will say is practical. A separate meter is not automatically bad — it separates the tenant’s bill from yours, which many owners want, and it is the only clean answer if the unit is ever to be separately conveyed under Government Code section 66342.
It is bad when it is imposed late, after a budget was built on shared service, and after the trench was priced. Ask early and ask in writing.
Where this becomes a safety question rather than a billing question
A shared service means the ADU’s branch circuits originate in the house’s panel or a subpanel fed from it. That arrangement is entirely ordinary and entirely code-compliant when a licensed contractor designs and installs it, with correct grounding and bonding, correct subpanel neutral–ground separation, and correct overcurrent protection.
It is dangerous when improvised. The failure that recurs in unpermitted ADU wiring is a subpanel with neutrals and grounds bonded together downstream of the service disconnect, which puts normal load current onto equipment grounding conductors.
It is invisible, it passes a plug-in tester, and it is one of the things a permit inspection is for. This is not a repair to attempt. It is a reason to permit the work.
The terms your contractor will use
- Load calculation
- The computation, performed under the California Electrical Code (Title 24, Part 3), of the demand load a service must carry, from the connected loads and the code’s demand factors. It is the document that answers whether a service upgrade is needed. It is prepared by a licensed contractor or an engineer, submitted with the permit application, and reviewed by the building department. We do not publish demand factors on this page because we did not retrieve the code text.
- Service versus panel
- The service is the utility’s supply to the property and the conductors and equipment to the main disconnect; the panel is the enclosure distributing branch circuits. Upgrading a panel does not upgrade a service, and a project that needs more capacity needs the service, the meter and often the utility’s own work — which is why “panel upgrade” quotes vary so widely.
- Electric-ready
- The 2022 Energy Code’s mandatory requirement, at sections 150.0(n) and 150.0(t)–(v), that a newly constructed building installing gas or propane space heating, water heating, cooking or clothes drying also install the dedicated circuits and reserve the panel space needed to replace those appliances with electric equipment later. The CEC states the intent plainly: “to facilitate future installations of high efficiency electric equipment and minimize future retrofit costs.”
- C-10 electrical contractor
- The California Contractors State License Board classification for electrical contracting. Service, panel, meter and branch-circuit work on a dwelling belongs to a licensee in this classification, working under permit. A license can be checked on the CSLB’s public register before you sign anything, and it should be.
- Point of delivery
- The boundary in the utility’s tariff between the utility’s facilities and the customer’s. Work on the utility’s side is the utility’s, on the utility’s schedule, at the charges in its filed rules. PG&E’s Electric Rule 16 governs the “Service Extension” from the distribution line to that point.
The line this page will not cross
Nothing on this page is instruction to perform electrical work, and it is not written so that it could be repurposed as such. There are no wire sizes, no torque values, no demand factors, no bonding diagrams, and there will not be.
Residential service and panel work is licensed, permitted and inspected in California for reasons that are written in coroner reports.
The specific hazards in ADU work are unremarkable and therefore easy to underestimate: service conductors that remain energised when every breaker in the house is off; a subpanel whose neutral and ground are improperly bonded; an existing 1960s panel with a bus that no longer accepts a listed breaker; aluminum branch-circuit conductors in mid-1970s stock terminated on devices not rated for them.
None of these is visible to a homeowner and all of them are ordinary findings for an electrician.
HyreADU recommendation: commission the load calculation first, before the architectural drawings are finished. It costs a fraction of a redesign, and it is the single cheapest way to find out whether the project you are imagining is the project your service can carry.
What we could not verify
The California Electrical Code text. Title 24, Part 3 is published under copyright and we did not retrieve it.
We therefore cite the load calculation by code part and by the Building Standards Commission’s published edition dates, and we quote no article, no demand factor and no table.
A page that quotes NEC demand factors it has not opened is a page to distrust.
The 2025 Energy Code’s electric-ready provisions. The California Energy Commission states that “[b]uildings whose permit applications are applied for on or after January 1, 2026, must comply with the 2025 Energy Code,” and that the update “expand[s] the use of heat pumps in newly constructed residential buildings, encourage[s] electric-readiness, strengthen[s] ventilation standards.” We could not retrieve the 2025 compliance manual, so every quoted requirement on this page is from the 2022 manual.
If your permit application is dated on or after 1 January 2026, confirm each requirement against the 2025 edition before relying on it.
Utility rules other than PG&E’s. We read PG&E Electric Rule 16 in full. We did not read Southern California Edison’s, San Diego Gas & Electric’s, LADWP’s or SMUD’s equivalents. Do not generalise the metering finding.
Any figure for how often an ADU triggers a service upgrade. We have not seen a dataset that answers it, and we are not going to estimate one. Permit records do not routinely record the existing service rating, which is the variable that would have to be joined.
Questions
Does building an ADU require an electrical panel upgrade?
Does an ADU need its own electric meter in California?
Is a gas ADU cheaper on electrical work than an all-electric one?
Do the electric-ready rules apply to a garage conversion ADU?
How many amps does an ADU need?
Can I run a subpanel to the ADU from the house panel myself?
My ADU was built before 2020 without permits. Will I have to rewire it?
Which Energy Code applies to my ADU?
Written and audited by
HyreADU Research Desk
Primary-source research, data analysis and fact checking
We are a research desk, not a builder. We read the permit extract, the statute, the HCD return or the fee schedule ourselves, and publish each figure with its source and retrieval date.
Where a number cannot be traced to a primary source, we leave it out and say what we could not verify. Our store-based claims cover California only.
- CA
- the only state this desk will make store-based claims about
- 5
- jurisdictions with extracted ADU permit evidence
- 735
- CSLB-verified companies in the California store
- 0
- national claims from a one-state store
How this desk works
- Primary sources only. Permit counts come from the city or county that issued the permit. Production counts come from HCD’s Annual Progress Report. Rents come from HUD or the Census. We do not cite an article that cites a source; we download the source and compute the figure ourselves.
- This is a California site. The company store is 734 California firms and one New Mexico firm. Permit evidence exists for five named jurisdictions: Los Angeles, San Francisco, Sacramento, San José and unincorporated Marin. A number from that store is titled to those places, never to the United States.
- A permit is not a completion, and a license is not an ADU grade. California licenses no ADU classification. Being named on an ADU permit is evidence of engagement in that jurisdiction, not of quality, completion, or work anywhere else. Owner-builder permits are excluded from contractor counts.
- Calculation is labeled as calculation. Figures we derive are never presented as something HCD, HUD, the Census or a city published. Terner Center research is cited as Terner’s, never restated as ours.
- We do not design, permit or build ADUs, and we take no payment for placement, ranking or a favorable mention. Pages that look like rankings are not: they publish public-record counts and let the reader decide.
- Nothing here is legal, tax or financial advice. Zoning, underwriting and appraisal practice vary by jurisdiction, lender and appraiser. The useful next step on a specific lot is the planning counter and a licensed professional.
Data as of California Energy Commission 2022 Single-Family Residential Compliance Manual (CEC-400-2022-006, May 2022) retrieved as PDF and text-extracted 2026-09-05; Government Code Chapter 13 sections retrieved from leginfo.legislature.ca.gov 2026-09-05; PG&E Electric Rule 16 (Advice 7572-E, effective 17 May 2025) retrieved as filed PDF 2026-09-05; code editions and effective dates from the California Building Standards Commission 2026-09-05. Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold.
Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
- California Energy Commission, 2022 Single-Family Residential Compliance Manual (CEC-400-2022-006), May 2022 , Retrieved as PDF and text-extracted on 2026-09-05. Chapter 10, “Electric Ready Requirements”, §§10.1–10.3.5 for the mandatory circuits, reserved breaker spaces and designated spaces quoted on this page, and for “[t]here are no electric ready requirements for additions or alterations.” Section 9.3.5 and Figure 9-2 for the ADU addition/newly-constructed-building classification. Chapter 7 for the photovoltaic provisions cited in our related solar study. Retrieved 2026-09-05.
- California Energy Commission — 2025 Building Energy Efficiency Standards , “Buildings whose permit applications are applied for on or after January 1, 2026, must comply with the 2025 Energy Code.” The 2025 update is described as expanding “the use of heat pumps in newly constructed residential buildings, encourag[ing] electric-readiness, strengthen[ing] ventilation standards, and more.” Retrieved 2026-09-05.
- California Building Standards Commission — California Building Standards Code editions and effective dates , Used to confirm the code vintages this page depends on. “The 2025 California Building Standards Code (Cal. Code Regs., Title 24) will be published July 1, 2025, with an effective date of January 1, 2026.” The 2022 edition “was published July 1, 2022, with an effective date of January 1, 2023.” Part 3 is the California Electrical Code; Part 6 is the California Energy Code. Retrieved 2026-09-05.
- Pacific Gas and Electric Company, Electric Rule No. 16 — Service Extensions , Revised Cal. P.U.C. Sheet No. 59584-E, Advice 7572-E, submitted 17 April 2025, effective 17 May 2025. B.3.a: “For revenue billing, electric service shall be individually metered to every residential unit in a residential building or group of buildings.” C.2: PG&E “will not normally provide more than one Service Extension … for any one building or group of buildings, for a single enterprise on a single Premises.” A.1: “PG&E will be responsible for planning, designing, and engineering its Service Extensions using PG&E’s standards for design, materials and construction.” Retrieved as the filed tariff PDF and text-extracted 2026-09-05. Retrieved 2026-09-05.
- California Government Code § 66311.5 — fees, connection charges and separate utility connections , (b) an ADU “shall not be considered … a new residential use for purposes of calculating connection fees or capacity charges.” (d) bars a required new or separate utility connection for the § 66323 by-right categories, with exceptions for construction with a new single-family dwelling and for separate conveyance. Added by renumbering § 66324 by Stats. 2025, Ch. 520, Sec. 7 (SB 543), effective 1 January 2026. Retrieved 2026-09-05.
- California Government Code § 66313 — definitions, including “permitting agency” , Subdivision (k) brings utilities inside the statute: a permitting agency is “any entity that is involved in the review of a permit … and for which there is no substitute, including, but not limited to, applicable planning departments, building departments, utilities, and special districts.” Retrieved 2026-09-05.
- California Government Code § 66323 — the by-right ADU categories , Defines which units section 66311.5(d) protects: conversions within a single-family dwelling’s proposed or existing space with expansion of “not more than 150 square feet”; one detached new-construction ADU of “not more than 800 square feet of livable space”; conversions within existing multifamily structures; and detached units on multifamily lots. Retrieved 2026-09-05.
- California Government Code § 66311.7 — permits for unpermitted units built before 1 January 2020 , Denial permitted only where “correcting the violation is necessary to comply with the standards specified in Section 17920.3 of the Health and Safety Code”; inspectors “shall not penalize an applicant”; no impact fees or connection or capacity charges “except when utility infrastructure is required to comply with Section 17920.3.” Added by renumbering § 66332 by SB 543, effective 1 January 2026. Retrieved 2026-09-05.
- California Health and Safety Code § 17920.3 — substandard building, including wiring , Subdivision (d): substandard includes “all wiring, except that which conformed with all applicable laws in effect at the time of installation if it is currently in good and safe condition and working properly.” Subdivision (h) covers fire hazard as determined by the fire chief or the chief’s deputy. Retrieved 2026-09-05.
- California Energy Commission, 2022 Building Energy Efficiency Standards Summary (CEC fact sheet) , Retrieved as PDF and text-extracted 2026-09-05. “The update also requires all new homes be electric-ready. That means buildings with gas stoves have the electrical panels and wiring to support a switch to electric stoves.” Used to corroborate the intent of the chapter 10 requirements quoted above. Retrieved 2026-09-05.
Get the load calculation before the drawings
A load calculation is the one document that answers this question for your property, and it costs a fraction of redesigning around an answer you discovered late. Commission it from a licensed C-10 electrical contractor or an electrical engineer, and check the license on the CSLB register first.
HyreADU does not design, permit or build accessory dwelling units, does not practice law, and does not perform electrical work. This page is informational and is not legal or engineering advice.
It describes what California code requires as retrieved on 5 September 2026; it is not instruction for performing electrical work and must not be used as such.
Electrical service, panel, meter and branch-circuit work on a dwelling in California is the work of a licensed C-10 electrical contractor, under permit and inspection. Service conductors remain energised when every breaker in the house is off.
The load calculation that answers the question on this page is property-specific and must be prepared by a licensed contractor or an electrical engineer.
Code editions change: everything quoted here from the Energy Code is from the 2022 edition, and the 2025 edition applies to permit applications submitted on or after 1 January 2026.