California Title 24 Explained: A Guide for New Multifamily and Commercial Developers

What is Title 24, Part 6?

California’s Title 24 Building Standards Code establishes the rules governing how buildings are designed and constructed across the state. Part 6 (also known as the California Energy Code) covers the energy-efficiency requirements for new and existing residential, multifamily, and commercial buildings. The current edition (the 2025 Energy Code) took effect January 1, 2026, and continues California’s push for building decarbonization through deeper electrification, encouraging more efficient heat pump technology, electric-ready infrastructure, stronger ventilation standards, and expanded requirements for solar and battery storage. The California Energy Commission (CEC) projects that the 2025 Energy Code will save $4.8B in energy costs and reduce GHG by about 4 million metric tons over its lifetime.

Does Title 24 Apply to My Project?

Title 24 applies to newly constructed buildings, additions, alterations, and accessory dwelling units (ADUs). The solar and storage mandates discussed in this guide, however, apply specifically to new construction. So if you’re a multifamily or commercial developer, the requirements below must be met. A building that doesn’t pass its final inspection means it cannot be legally occupied. 

Does My Project Need Solar?

For most new multifamily and commercial buildings in California—yes. 

Nonresidential Buildings. Under Section 140.10(a) of the Building Code, a solar photovoltaic (PV) system is required for all newly constructed nonresidential building types listed in the table below: