When did the Title 24 energy standards start?

The first standards were in force by 1978, under authority the Warren-Alquist Act of 1974 gave the Energy Commission.

How often is the Energy Code updated?

Every three years. The 2022 code applied to permit applications from 1 January 2023, and the 2025 code to applications from 1 January 2026.

When did solar become required on new homes?

With the 2019 Energy Code, which took effect on 1 January 2020 and added a prescriptive photovoltaic requirement for new low-rise residential buildings.

Why do sources give different start dates?

Energy Commission documents give different years, from 1976 to 1978, for when the first standards were adopted. They agree the standards were in effect in 1978.

A Short History of the Title 24 Energy Code

California's building energy standards come from the Warren-Alquist Act of 1974, which created the Energy Commission and told it to set them; the first standards were in force by 1978. The code has been revised many times since, now on a three-year cycle, and the 2025 Energy Code has applied to permit applications since 1 January 2026.

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The start: 1974 to 1978

The Warren-Alquist Act passed in 1974 and set up the State Energy Resources Conservation and Development Commission, now the Energy Commission, which began work in 1975. The Act charged it with adopting and maintaining energy standards for new buildings and told local building departments not to approve permits until a building met them. It also set the test that still governs every cycle: the standards must be cost-effective "when taken in their entirety and amortized over the economic life of the structure".

In 1975 the Department of Housing and Community Development adopted rudimentary energy conservation standards under the State Housing Law, as a precursor. The Commission's own standards took effect in 1978, in the aftermath of the 1973 oil embargo. Commission documents give different years for the first adoption vote, the 2025 Standards' abstract saying 1976, but they agree that the standards were in effect in 1978.

Second generation and consolidation

Second-generation nonresidential standards took effect for offices in 1984 and for retail and wholesale stores in 1985. The 1992 revision simplified and consolidated the requirements for all building types, with major changes to lighting, envelope, fenestration and HVAC, and the Commission credits it with leading the way for national standards in other states. After minor revisions in 1995, the 1998 standards cut lighting power limits sharply, because electronic ballasts and T-8 lamps had become cost-effective.

2001: an emergency rewrite

The electricity crisis of 2000 brought rolling blackouts. The Legislature responded with Assembly Bill 970, which required an emergency update within 120 days. The resulting 2001 standards, often called the AB 970 Standards, took effect in mid-2001 and brought high-performance windows throughout California and stricter lighting rules.

Widening the scope

The 2008 code added refrigerated warehouses and steep-sloped roofs. The 2013 code brought in covered processes, from parking garage ventilation and compressed air to commercial kitchens and data centres, and set the first mandatory insulation minimums for nonresidential buildings. The Commission describes the 2016 code as current with ASHRAE 90.1; see Title 24 vs ASHRAE 90.1.

Solar, heat pumps and a new verification programme

The 2019 code, effective on 1 January 2020, made solar photovoltaics a prescriptive requirement for new low-rise residential buildings, based lighting on LEDs and brought healthcare facilities into scope for the first time. The 2022 code, for applications from 1 January 2023, encouraged heat pumps, made new homes electric-ready, expanded solar and battery requirements and restructured the multifamily rules into their own sections.

The Commission adopted the 2025 code on 11 September 2024, and the Building Standards Commission approved it on 17 December 2024. In force since 1 January 2026, it makes heat pumps the prescriptive baseline for both space and water heating in new homes, and it moved the HERS field verification rules into Part 1 as the Energy Code Compliance (ECC) Program, so HERS raters became ECC-Raters. The changes are summarised in 2025 Energy Code changes and the ECC Program.

How a cycle runs

Each update starts with measures evaluated by Commission staff and consultants, then workshops and public comment. The Commission adopts the standards, the Building Standards Commission approves them as part of Title 24, compliance manuals follow within 180 days, and there is about a year of training before the effective date. Which edition applies to a project depends on the date its permit application was submitted, as what Title 24 is explains.