California’s 2025 Energy Code took effect January 1, 2026, replacing the 2022 cycle and changing how solar PV and battery storage are sized for new construction. Every permit application submitted on or after that date must use the 2025 requirements, compliance software, and forms rather than the 2022 code cycle.

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Yes. Solar PV is generally required for newly constructed single-family homes, low-rise and high-rise multifamily buildings, and specified nonresidential buildings under the 2025 California Energy Code (Title 24, Part 6). The exact requirement depends on building type, the permit application date, available roof area, the compliance method used, and any applicable exceptions. Existing homes are not required to add solar solely because of the statewide new-construction mandate.

The “California solar mandate” refers to the photovoltaic requirements built into Title 24, Part 6, the state’s Building Energy Efficiency Standards. It is not a single freestanding law but a set of standards adopted and updated every three years by the California Energy Commission (CEC). The original PV requirement took effect January 1, 2020, for single-family homes and low-rise multifamily buildings up to three stories, and has since been extended to high-rise multifamily and specified nonresidential building types.

Compliance is not always “put a standard array on every roof.” Depending on the project, a building can satisfy the mandate through prescriptive PV sizing, a performance-based compliance path, a reduced PV size tied to available roof area, a qualifying exception, or, where approved, a community solar offset.

A few changes matter most for solar and storage design work:

Permit date determines the code cycle. The version of Title 24 that applies is set by the building permit application date, not the construction start date or when design work began. Applications submitted before January 1, 2026 may still use the 2022 code; anything submitted on or after that date must meet the 2025 standards.

Updated PV sizing inputs. The Solar Access Roof Area (SARA) multipliers and the climate-zone-based equations were revised, so a home that met the 2022 sizing requirement may calculate differently under the 2025 code. See the sizing methodology below.

Expanded battery scope. More nonresidential building types, including assembly, worship, and laboratory occupancies, now fall under combined solar-plus-battery requirements, and the linkage between PV size and required battery capacity was tightened for buildings already subject to storage rules.

Electrification and load coordination. The 2025 code expands heat pump use and electric-readiness provisions, which vary by building type, climate zone, and compliance path. These changes can shift a project’s modeled annual load and future electrical demand, which in turn affects service sizing. Coordinate with the project’s energy consultant rather than carrying forward 2022 compliance-model assumptions.

This table reflects general prescriptive-path treatment. Confirm specifics against the applicable compliance manual and local jurisdiction amendments before finalizing a design.

For single-family and low-rise multifamily buildings, the required PV system size is the smaller of two results, calculated under Section 150.1(c)14 for single-family and Section 170.2(f) for low-rise multifamily:

Solar Access Roof Area (SARA) method: usable SARA square footage multiplied by 18 watts per square foot for steep-sloped roofs, or 14 watts per square foot for low-sloped roofs. SARA excludes areas with less than 70 percent annual solar access, occupied roof areas, and roof area unavailable due to other code requirements.

Equation method (Equation 150.1-C for single-family, Equation 170.2-C for low-rise multifamily): based on climate zone, conditioned floor area, and number of dwelling units.

Whichever of the two produces the smaller system size is the requirement. In practice, the equation-based result usually governs on a typical residential roof, while the SARA calculation acts as a ceiling on very small or heavily shaded roofs. Nonresidential and high-rise multifamily buildings follow the same smaller-of-two logic under Section 140.10(a), using their own building-type equations.

Worked example, illustrative only: a single-family home with 1,200 square feet of usable steep-sloped SARA has a roof-area ceiling of 1,200 x 18W = 21.6 kWdc, far above what a typical home needs. The equation-based result, driven by climate zone, conditioned floor area, and dwelling count, will almost always be the smaller and therefore controlling figure for a standard-sized home. Run the project’s actual inputs through CEC-approved compliance software (CBECC-Res) rather than estimating by hand, since the equation coefficients vary by climate zone.

Battery reduction: for single-family homes, the calculated PV size under Equation 150.1-C can be reduced by 25 percent if installed with a qualifying battery storage system. The battery must meet Joint Appendix JA12 qualification requirements and have a minimum battery compliance cycling capacity of 7.5 kWh.

It depends on building type:

• Single-family: not required outright. Newly constructed one- and two-dwelling-unit buildings generally must meet the battery-ready wiring requirements in Section 150.0(s), covering panel capacity and a dedicated backup path, but only when the load-serving entity provides electrical service greater than 125 amps, subject to an exception. Installing a qualifying battery now, instead of just wiring for one later, is what unlocks the 25 percent PV size reduction.

• Low-rise multifamily (up to 3 stories): PV is required under Section 170.2(f). No dedicated battery-ready mandate parallel to the single-family 125-amp rule was identified for this category in the 2025 code; confirm project-specific requirements with the applicable compliance manual.

• High-rise multifamily (4 or more stories): battery storage is required under Section 170.2(h) whenever the building is subject to the PV requirement, unless the project meets one of two exceptions, including one where the installed PV system is under 15 percent of the capacity calculated under Equation 170.2-D.

Qualifying nonresidential: battery storage is often required alongside PV under Section 140.10(a), sized using building-specific equations, not simply “encouraged.”

A newly constructed detached ADU generally requires new PV capacity sized for the ADU; existing PV serving the primary residence cannot, by itself, satisfy that separate requirement. Those new modules may be installed as a standalone system or added to an existing PV system elsewhere on the same residential lot, subject to utility and code requirements; they don’t necessarily need a dedicated meter. Local jurisdiction amendments can affect specifics, so confirm before finalizing plans.

Not every project that appears exempt actually is; in many cases the code reduces the required system size rather than eliminating the requirement outright. For single-family buildings, Section 150.1(c)14 lists five exceptions:

No PV system is required if the usable SARA is less than 80 contiguous square feet. No PV system is required if the calculated minimum PV system size is less than 1.8 kWdc. No PV system is required if the enforcement authority determines the system cannot meet ASCE 7-16, Chapter 7 snow-load requirements. Buildings approved by the local planning department before January 1, 2020, with mandatory conditions of approval limiting PV, may qualify for reduced sizing. A qualifying battery storage system can reduce the calculated PV size by 25 percent rather than eliminating the requirement.

Multifamily and nonresidential buildings have their own, separately listed exceptions, including minimum roof-area and minimum system-size thresholds and, for some building types, areas without virtual net energy metering compensation. Community solar can also substitute for an on-site system where the CEC has approved a program for that building type and utility service area. Confirm which exception list applies to the specific building type rather than assuming the single-family exceptions carry over.

• Building permit application date, which sets the applicable Energy Code cycle

• Occupancy and building height category, which determines which requirement set applies

• Prescriptive or performance compliance path

• Equation-based PV size calculation

• SARA-based PV size calculation, using the smaller of the two results

• Applicable exceptions, documented

• Battery storage or battery-ready requirement, determined by building type

• PV layout and roof plan

• Structural review for roof-mounted systems

• Electrical one-line diagram and equipment specifications

• Rapid shutdown compliance details

• Fire access and setback requirements

• CF1R and related energy compliance documentation

• Interconnection documentation

• Battery documentation, including JA12 qualification, when applicable

• Certificates of installation and acceptance at project close-out

The Solar Billing Plan (NEM 3.0), administered by the California Public Utilities Commission, compensates exported solar generation at rates tied to the Avoided Cost Calculator, well below the retail-rate credit under legacy NEM 2.0. The core issue is not that midday electricity is simply cheap; it is that exported solar earns relatively low compensation during most production hours, while imported power during evening peak periods, typically 4 to 9 p.m. under common Time-of-Use schedules, can be expensive.

That gap is what makes self-consumption and storage design decisions, and not just meeting the minimum PV size, the main lever for a homeowner’s actual bill savings.

Practical design takeaways for mandated systems:

Avoid sizing solely around annual export value. Model expected onsite consumption rather than assuming excess generation will be worth what it once was. Account for typical evening peak periods under the applicable utility’s Time-of-Use schedule. Make electrical and site plans battery-ready even when a battery is not being installed at the outset. Factor in load shifting, EV charging, and heat pump loads when estimating future demand. Confirm utility-specific Solar Billing Plan requirements, since implementation details vary by utility.

A few incentive changes affect how mandated projects pencil out for homeowners in 2026:

• The federal residential credit has ended. The Residential Clean Energy Credit (Section 25D) expired for systems placed in service after December 31, 2025. Direct-purchase and loan-financed systems installed in 2026 no longer qualify.

• Third-party ownership is the remaining federal pathway, with caveats. Leases and PPAs may still access a credit through the Section 48E business investment tax credit, but eligibility now involves timing rules, ownership structure, and, for larger projects, prevailing wage, apprenticeship, domestic content, and prohibited foreign entity considerations. Treat 48E as a pathway to evaluate case by case, not a guaranteed 30 percent, and consult a tax professional for project-specific guidance.

• SGIP still covers battery storage. California’s Self-Generation Incentive Program continues to offer battery rebates, allocated regionally by utility.

• The property tax exclusion sunsets January 1, 2027. California’s active solar energy system provision, under Section 73 of the Revenue and Taxation Code, is a new-construction assessment exclusion, not a general property tax exemption. It prevents the added value of a mandated solar system from triggering a reassessment. Eligibility and filing requirements, including rules for the initial purchaser of a new home, should be confirmed with the county assessor, particularly for systems built into homes sold to a buyer.

Whether you’re a solar contractor looking for fast, code-compliant permit plan sets or a homeowner in need of expert solar repairs or upgrades, GreenLancer has you covered. Our U.S.-based team and nationwide network of licensed professionals deliver reliable support for every stage of your solar projects.

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Generally yes, for newly constructed single-family homes and most multifamily buildings, sized under the 2025 Title 24 Energy Code, unless the project qualifies for a specific exception.

No. The mandate applies to new construction. Existing homes are not required to add solar because of the statewide new-construction rule, though separate local or utility programs may apply in specific cases.

Generally no for routine alterations. The PV mandate is tied to new construction; additions and alterations are typically evaluated differently than a newly constructed building.

Newly constructed detached ADUs are generally required to include solar PV. Attached ADUs, additions, garage conversions, and JADUs built within an existing structure are generally treated as alterations and are not subject to the new-construction PV trigger.

Not universally. A battery itself is not mandatory for single-family homes, but newly constructed one- and two-dwelling-unit buildings with electrical service over 125 amps generally must include battery-ready wiring if no battery is installed. High-rise multifamily and many qualifying nonresidential buildings face a prescriptive battery requirement alongside PV, subject to specific exceptions.

The version of Title 24 that applies is determined by the building permit application date. Projects permitted on or after January 1, 2026 must meet the 2025 Energy Code; projects permitted before that date may still use the 2022 code.

As the smaller of two results: a Solar Access Roof Area calculation (18 watts per square foot for steep-sloped roofs, 14 watts per square foot for low-sloped roofs) and a climate-zone and floor-area-based equation. For single-family homes, no PV system is required if that calculated result is less than 1.8 kWdc, and a qualifying battery can reduce the equation-based result by 25 percent.

In some cases. Where the CEC has approved a community shared solar program for a building type and utility service area, subscribing to it can substitute for an on-site PV system under the performance compliance approach.