California Energy Code

The California Energy Code is Part 6 of the California Building Standards Code (Title 24, California Code of Regulations) — commonly called the Title 24 energy code or simply Title 24, Part 6. It sets minimum energy-efficiency standards for the building envelope, HVAC, lighting, water heating, solar photovoltaics and battery storage in both residential and nonresidential buildings. Unlike most other parts of Title 24, it is developed by the California Energy Commission (CEC) rather than reprinting a model code, and applies across California's 16 climate zones.

The 2025 California Energy Code is the current edition, effective January 1, 2026, replacing the 2022 edition. Each three-year cycle tightens efficiency and expands electrification — the 2025 update strengthens heat-pump baselines for space and water heating and broadens solar PV plus battery energy storage requirements to more building types. Because local jurisdictions may adopt reach codes that go further, the requirements for your project depend on the adopted edition and local amendments — which is exactly what GoCodebook reconciles for you.

The code is organized by who the building serves, not by building system. Sections in the 100s and 110s apply to all occupancies; the 120s–140s are nonresidential and hotel/motel; the 150s are single-family residential; the 160s and 170s are multifamily; and the 180s cover multifamily additions and alterations. Finding the right series first is most of the work.

Title 24, Part 6 governs how efficiently a building uses energy. Core areas include the building envelope (insulation, fenestration U-factor/SHGC, air sealing and cool roofs), HVAC efficiency, sizing and duct sealing, lighting power and controls, water heating (with a strong push toward heat-pump water heaters), and on-site solar PV generation paired with battery storage. Requirements vary by climate zone — your zone depends on the project address, not just the city.

Compliance can be demonstrated two ways: the prescriptive path (meet each component requirement) or the performance path (model the whole building against an energy budget using CEC-approved software). The Energy Code works hand-in-hand with the California Mechanical Code (Part 4) for HVAC installation and the California Plumbing Code (Part 5) for water-heating piping.

The 2025 cycle expands the solar PV mandate and now pairs it with battery energy storage for many building types — including low-rise and high-rise multifamily, hotels/motels, and nonresidential occupancies such as offices, retail, schools, grocery, restaurants and warehouses that meet roof-area minimums. Storage is sized by the Energy Code's equations, and pairing qualifying storage can reduce the required PV size. The code also tightens heat-pump baselines and now requires third-party refrigerant-charge verification across climate zones.

These provisions are some of the most-searched Title 24 topics because they drive cost and design early. Rather than parsing the regulation text, ask GoCodebook whether PV and storage are required for your occupancy and climate zone and get the controlling section with a citation. See where coverage is deepest.

Residential projects document compliance with a set of registered forms: the CF1R (Certificate of Compliance) prepared during design, the CF2R (Certificate of Installation) completed by the installing contractor, and the CF3R (Certificate of Verification) completed by a third-party HERS rater for field testing such as duct leakage and refrigerant charge. Nonresidential projects use the parallel NRCC/NRCI/NRCV forms. These are typically required before permit and at final inspection.

The Energy Commission sets the statewide standard, but cities and counties can adopt reach codes that exceed it — for example all-electric or higher-efficiency requirements. GoCodebook identifies the adopted edition and local amendments for your address and returns the governing provision with a citation. For green-building overlap, also check CALGreen (Part 11).

Once you know which series applies, the sub-number tells you the compliance path. For single-family work, Section 150.0 holds the mandatory features and devices every project must meet, Section 150.1 holds the performance and prescriptive approaches for new construction, and Section 150.2 covers additions and alterations — the section most remodels actually live in.

Multifamily buildings got their own series in the 2022 cycle and keep it in 2025: Section 160.x for mandatory requirements, Section 170.x for the performance and prescriptive approaches, and Section 180.x for additions, alterations and repairs. Nonresidential work uses Section 120.x for mandatory mechanical and ventilation, Section 130.x for lighting, and Section 140.x for the compliance approaches.

Sections 110.0 through 110.x apply to everyone — appliance efficiency, space-conditioning equipment, service water heating, pools and spas — because they regulate the equipment itself rather than the building type it is installed in.

Most Energy Code questions are not about new buildings. An addition, a re-roof with new insulation, a window replacement, a new HVAC system or a panel upgrade each triggers a defined subset of requirements rather than a whole-building upgrade. For single-family that subset is in Section 150.2; for multifamily it is Section 180.x; for nonresidential it is Section 141.x.

Two rules catch people out. Replacing HVAC equipment usually triggers duct sealing and HERS verification, and in many climate zones also refrigerant charge verification — field tests that must be scheduled before the system is concealed. And an alteration that increases conditioned floor area can convert the project from an alteration into an addition, changing the applicable section entirely.

Because the Energy Code is verified in the field rather than only on paper, the HERS rater is effectively part of the construction schedule. Registering the CF2R and completing the CF3R late is one of the most common causes of a delayed final inspection.

California's adopted codes — including the California Energy Code — are published under Title 24 and hosted on code libraries such as UpCodes (up.codes) and ICC Digital Codes from the International Code Council (ICC). Those let you read the text section by section.

GoCodebook goes further: instead of searching a code library, you ask a question and get the controlling provision for the edition and local amendments your jurisdiction adopted, with a citation to verify. See how GoCodebook compares to UpCodes and ICC.