A project is Title 24 compliant when it meets California’s Energy Code, which is Part 6 of Title 24 of the California Code of Regulations. The California Energy Commission writes and updates these standards, and the current version — the 2025 Energy Code — took effect January 1, 2026, and applies to all new construction and major renovations statewide.1California Energy Commission. California’s Energy Code Update Guides the Construction of Cleaner, Healthier Buildings Compliance is not a declaration. It is a design calculation, a paper trail, and, for many measures, a field test by a certified rater.
What Title 24 Compliance Actually Means
Title 24 is the entire California Building Standards Code, split into 12 parts covering structural safety, plumbing, fire protection, and more.2Department of General Services. Title 24 Building Standards Code as Adopted by the Division of the State Architect In construction conversation, though, “Title 24 compliant” almost always refers to Part 6, the California Energy Code, which governs how efficiently a building uses energy.3California Energy Commission. Building Energy Efficiency Standards A related section, Part 11 (CALGreen), sets broader green building standards and includes some voluntary energy measures that go beyond the Energy Code baseline.4Department of General Services. Codes – DGS When your architect, contractor, or plan checker says they need Title 24 documentation, they mean Part 6.
The code’s reach is tied to geography. California divides the state into 16 climate zones, and envelope specs, window ratings, and energy budgets all shift by zone.5California Energy Commission. Climate Zone Tool, Maps, and Information Supporting the Building Energy Efficiency Standards A home on the foggy San Francisco coast faces different requirements than one in the Palm Springs desert. The CEC publishes an online tool to identify a project’s zone by address. Get this wrong at the start, and the calculations downstream are wrong too.
The Two Ways to Prove Compliance
The Energy Code offers two compliance paths — performance or prescriptive — layered on top of mandatory measures that apply to every building regardless.6California Energy Commission. 2025 Building Energy Efficiency Standards for Residential and Nonresidential
The performance approach gives the whole building an energy budget. You run the design through CEC-approved modeling software, and if the model shows the building uses no more energy than a hypothetical code-compliant version of itself, you pass. This path lets designers trade off between components. Thinner wall insulation can be offset by better windows, or a less efficient envelope by a stronger HVAC system. The CEC publishes free, public-domain software for this.
The prescriptive approach is a checklist. Each component — windows, insulation, HVAC equipment, lighting — must independently meet a specified minimum. No tradeoffs. If the code calls for R-13 walls in your climate zone, R-13 is what you install. Simpler projects often take this path because energy modeling would be overkill.
Mandatory measures apply under either path. Duct sealing, specific ventilation rates, and proper equipment sizing are examples. You can’t model your way around them.
What the Code Regulates
Building Envelope
Roofs, walls, floors, windows, and doors must meet minimum R-values for insulation and maximum U-factors and Solar Heat Gain Coefficients for glazing. Lower U-factor means less heat escapes or enters through the glass; lower SHGC means less solar radiation gets in. The 2025 code raised efficiency expectations for exterior walls and windows, and for multifamily buildings, slab edge insulation.1California Energy Commission. California’s Energy Code Update Guides the Construction of Cleaner, Healthier Buildings Quality Insulation Installation (QII) verification by a certified rater during framing can earn performance credit beyond simply hitting minimum R-values.
HVAC Systems
Heating, cooling, and ventilation equipment must hit minimum efficiency ratings and be sized correctly for the building. Oversized equipment short-cycles, wastes energy, and causes comfort problems. Ducts must be sealed and tested against leakage thresholds. The 2025 code effectively builds its energy budgets around heat pumps for both space heating and cooling, making them the baseline assumption for new construction.1California Energy Commission. California’s Energy Code Update Guides the Construction of Cleaner, Healthier Buildings Smart thermostats that respond to time-of-use electricity pricing are part of updated controls requirements.
Water Heating
Water heaters are rated by Uniform Energy Factor (UEF), which replaced the older Energy Factor metric.7California Energy Commission. 2022 Water Heater Efficiency Guide Higher UEF means more fuel input converts to hot water. The 2025 code builds the energy budget around heat pump water heaters, particularly in low-rise multifamily buildings with individual units.
Lighting
Indoor and outdoor lighting are regulated by power density — the maximum watts allowed per square foot for a given space type. Controls carry as much weight as the fixtures: occupancy sensors, daylight-responsive dimming, and automatic shut-off are required in various applications.
Solar PV and Battery Storage
Since 2020, all newly constructed single-family homes in California must include a solar photovoltaic system, and the 2025 code carries that mandate forward.8California Energy Commission. 2025 Single-Family Solar PV Minimum system size is the smaller of two calculations: one based on available solar roof area, and one based on climate zone, conditioned floor area, and number of dwelling units. Limited exceptions apply when the solar-accessible roof area is under 80 contiguous square feet, when the calculated system would be under 1.8 kilowatts, when the local authority finds snow loads can’t be met, when the project had pre-2020 planning approval with mandatory conditions, or when a qualifying battery storage system of at least 7.5 kWh usable capacity is paired with the solar (which reduces the required system size by 25 percent).
Battery storage is also now a prescriptive requirement for newly constructed nonresidential buildings that require solar PV, including offices, retail, schools, restaurants, hotels, and multifamily buildings with three or more habitable stories.9California Energy Commission. 2025 Nonresidential Battery Energy Storage System (BESS) Required capacity is calculated from formulas tied to conditioned floor area and building type. Additions and alterations to existing buildings are exempt from the battery requirement.
Electric-Ready Wiring
Even when a new building installs gas appliances, the 2025 code requires it to be wired for an eventual electric conversion. The point is to avoid expensive retrofits by running circuits and reserving panel space up front. For nonresidential and multifamily buildings, that means a dedicated 240-volt, 30-amp minimum branch circuit within 3 feet of any gas furnace (with panel space reserved and labeled “For Future 240V use”), a 240-volt, 50-amp minimum circuit within 3 feet of any gas cooktop, and a 240-volt, 30-amp minimum circuit within 3 feet of each gas dryer.10California Energy Commission. 2025 NRCI-ELC-E Electric Ready Requirements EV charging access in multifamily developments was also strengthened under the 2025 code.1California Energy Commission. California’s Energy Code Update Guides the Construction of Cleaner, Healthier Buildings
When the Rules Apply to Your Project
Every new residential and nonresidential building in California must fully comply with the current Energy Code.3California Energy Commission. Building Energy Efficiency Standards For existing buildings, what you’re doing determines what applies:
- Additions are treated like new construction. The new square footage must meet all current standards.
- Alterations trigger current efficiency standards for whatever is replaced or upgraded — a new HVAC system, new windows, a new roof. A major alteration can sometimes pull related, untouched components up to current code as well.
- Repairs that don’t increase energy consumption are generally exempt.
A qualified historic building can be fully exempt, but the deciding factor is registration, not age. The building must be listed on the State or National Register of Historic Places, designated as historic under local or state law, certified as eligible for listing by the State Historic Preservation Officer or the Keeper of the National Register, or qualify as a contributing resource within a designated historic district.11U.S. Department of Energy – Office of Critical Materials and Energy Innovation. What Is Required for Historic Buildings? If you think your building qualifies, confirm with your local jurisdiction before assuming the exemption.
One narrow carve-out: Executive Order N-29-25 temporarily suspends the 2025 update for projects involving repair or replacement of residential structures damaged or destroyed by the 2025 Los Angeles area wildfires. Those projects must still be solar-ready but are exempt from solar and battery storage requirements.1California Energy Commission. California’s Energy Code Update Guides the Construction of Cleaner, Healthier Buildings
How Compliance Gets Documented and Verified
Three forms carry the compliance paper trail:
- CF1R (Certificate of Compliance) is prepared at the design stage. It contains the building’s energy calculations and shows that the design meets code.
- CF2R (Certificate of Installation) is completed by the installing contractor and confirms that components were installed as specified in the CF1R.
- CF3R (Certificate of Verification) is completed after field testing by a certified rater and verifies that installed systems perform as claimed.12California Energy Commission. 2025 Energy Code Compliance Documents – Forms for Single-Family Buildings
Energy consultants or mechanical engineers typically prepare the CF1R and run the compliance software; architects integrate the results into construction documents. For smaller residential projects, compliance documentation starts around $300 and climbs with square footage and complexity. Errors in the CF1R cascade through the project, so this is not the place to cut corners.
Under the 2025 code, the former HERS Raters are now Energy Code Compliance (ECC) Raters, and the oversight program is the ECC Program.13California Energy Commission. Energy Code Compliance Program When the CF1R flags measures that require field verification, an ECC-Rater performs diagnostic testing and visual inspection. Common tests include duct leakage, refrigerant charge, HVAC airflow, building envelope air leakage, and insulation installation quality. If a test fails, the contractor must correct the system and retest until it passes. ECC verification fees for residential projects typically run $250 to $400 depending on tests required and home size.
Before construction, the local building department runs a plan check against the submitted compliance documents. During and after construction, on-site inspections confirm that installed components match the approved plans. Projects requiring field verification must submit CF3R forms registered with an ECC Provider before receiving final approval.12California Energy Commission. 2025 Energy Code Compliance Documents – Forms for Single-Family Buildings
What Non-Compliance Costs You
The most immediate consequence is that the local building department will not sign off. No approved compliance documents, no final inspection. No final inspection, no certificate of occupancy. You cannot legally occupy or use the building.
If inspectors catch violations mid-construction, a stop-work order can halt the project until the issues are fixed. Depending on how far work has progressed, remediation can mean tearing out finished surfaces to replace non-compliant insulation, windows, or ductwork. The California Energy Commission also has authority to impose administrative civil penalties for Energy Code violations. And because compliance documentation becomes part of the building’s permanent record, non-compliant work creates liability exposure when the property is later sold.
Budget for a qualified energy consultant and ECC-Rater verification from day one, and treat the CF1R as a design document that drives construction, not paperwork to scramble for at the end.