California Title 24 Part 6 Commercial Solar Requirements 2026

California's Title 24 Part 6 Energy Code has required solar on new residential construction since 2020. The 2025 Energy Code — effective for permits pulled after January 1, 2026 — expands the mandate to cover most new nonresidential buildings. That's offices, retail, schools, restaurants, warehouses, distribution centers, and more. If you're developing commercial real estate in California in 2026, solar + battery storage is no longer optional for most project types.

What Changed in the 2025 Code

The 2022 Energy Code introduced commercial solar requirements for specific building types. The 2025 Energy Code expands the list significantly. Covered nonresidential building types now include:

• •Offices
• •Retail (general merchandise, grocery, etc.)
• •Schools (K-12 and higher ed)
• •Restaurants
• •Warehouses and distribution centers
• •Additional occupancy classes added in 2025 (see current CEC docs for full list)

Battery storage is mandatory wherever PV is required. This is the major change from prior code versions — it's no longer just solar; it's solar + storage.

How PV Sizing Is Calculated

Title 24 offers two methods for determining required PV system size:

1. Capacity-factor method. The code specifies a minimum PV capacity based on the building's conditioned floor area and occupancy type. Each building type has its own factor.

2. Solar Access Roof Area (SARA) method. Applies a PV wattage per square foot of qualifying roof area: approximately 14-18 W/sf depending on roof slope. Flat or low-slope roofs generally fall in the higher end of the range.

Mixed-occupancy buildings (e.g., retail on ground floor + office above) have specific rules for apportioning the PV requirement across occupancy classes. Your project architect and energy consultant handle the calculation; verify it's correct before permits are pulled because errors are expensive to fix post-construction.

Battery Storage Sizing

Wherever PV is required, battery storage is now required alongside it. Sizing methodology follows the 2025 code's specific rules based on PV capacity and building type. The battery is intended to enable load-shifting and reduce peak-hour grid draw — aligning with California's grid-reliability goals and the NEM 3.0 / Net Billing Tariff economics that already favor on-site storage.

What About Existing Commercial Buildings?

Title 24 Part 6 is a new-construction and major-renovation code. Existing commercial buildings that aren't being permitted for substantial alteration are not subject to the new PV + storage mandate. That said, if you're doing a significant tenant improvement, addition, or reroof, Title 24 alteration requirements may trigger PV or efficiency upgrades depending on scope — check with your project architect.

Practical Implications

For developers planning California commercial projects permitted in 2026 and beyond:

• Budget for PV + battery from day one. The mandate adds meaningful cost — typically $100K-$500K+ on mid-size commercial projects depending on building size. Baking it into the pro-forma at design rather than treating it as a surprise change-order is essential.
• Choose a commercial EPC with Title 24 expertise. The sizing, interconnection, and Title 24 compliance documentation is specialized work. EPCs that regularly handle commercial new construction (as opposed to retrofit-only installers) will have the workflow down.
• Consider oversizing for operational benefit. The code specifies a minimum PV + battery size. Going meaningfully larger can reduce your building's operating energy cost substantially, especially given California commercial rates and TOU structures. The incremental cost per watt on a larger system is lower than on the code-minimum-only install.
• Don't forget the 30% ITC. Even though the solar is code-required, the federal Investment Tax Credit still applies to the full system cost. Same with MACRS depreciation. Title 24 compliance and federal tax incentives are independent — you get both.

Frequently Asked Questions

Does Title 24 require solar on all new California commercial buildings?

Most, but not all. The 2025 Energy Code expanded the covered occupancy classes to include most common commercial building types — offices, retail, schools, restaurants, warehouses — but some specialty categories are still exempt. Check the current CEC Title 24 documentation for your specific project type.

When does the 2025 Energy Code take effect?

Permits pulled after January 1, 2026 are subject to the 2025 Energy Code. Projects with permits submitted before that date remain under the 2022 Energy Code.

Is battery storage really mandatory?

Yes, wherever PV is required under the 2025 code, battery storage is also required. This is the biggest change from the 2022 code.

Can I still claim the federal tax credit on Title-24-required solar?

Yes. The federal Investment Tax Credit (30% base through 2032) applies regardless of whether the solar is code-required or voluntary. Same with 5-year MACRS depreciation. Title 24 compliance and federal incentives don't conflict.