Window Replacement in California: CSLB Licenses and Title 24

In California, most window replacement jobs call for a contractor license from the Contractors State License Board (CSLB). Since January 1, 2025, an unlicensed person may take on a project only if the total price for labor, materials and everything else is under $1,000, no workers are hired and no building permit is needed; a smaller job that needs workers or a permit still requires a license in the appropriate classification (CSLB announcement of AB 2622; CSLB license check) ¹⁴. A whole-house window job is far above that line.

The other California-specific rule is the state Energy Code, Title 24, Part 6. It sets U-factor and solar heat gain limits for replacement windows that depend on which of California's 16 building climate zones the house is in (California Energy Commission, Title 24) ⁵⁷.

The CSLB license and the $1,000 line

The threshold used to be $500. Assembly Bill 2622, effective January 1, 2025, raised it to $1,000, and the $1,000 includes all costs of the project (CSLB AB 2622 release) ¹. An unlicensed person who advertises for this small work must say in the advertisement that they are not licensed ¹.

The CSLB's release also lists the penalties for unlicensed contracting: administrative fines of up to $15,000, jail sentences of up to six months and fines up to $5,000, with heavier penalties for repeat offenders ¹. The same release advises that a down payment on a home improvement project should not exceed 10 percent of the contract price, and that later payments should not run ahead of the work completed or materials delivered (CSLB AB 2622 release) ¹.

Which license classification fits window work

The CSLB's classification guide describes the C-17 Glazing contractor as one who selects, cuts, assembles and installs all kinds of glass and glass work, and fabricates and glazes frames, panels, sashes and doors, and installs these items in any structure (CSLB description of classifications) ².

For a project that combines windows with other work, you may also see a Class B General Building contractor. The guide describes the B license as covering work on structures that requires at least two unrelated building trades or crafts ². If a window-only job is quoted by a B contractor, ask how the job fits that classification.

How to check a California license

The CSLB's license check looks up a contractor license or a Home Improvement Salesperson registration, and the board's page on hiring a contractor page links to it ³⁴. Is the installer licensed in the right classification? Before you sign, check:

• that the license number on the quote matches the business name on the CSLB record;
• the classification (C-17, or B for a larger project);
• that the license is active;
• that the salesperson who visits is registered, if they are not the contractor ⁴.

Title 24 and replacement windows

California's Building Energy Efficiency Standards, Title 24 Part 6, are updated every three years (California Energy Commission) ⁵. The 2025 Energy Code applies to buildings whose permit applications are filed on or after January 1, 2026 (2025 standards page) ⁶.

The Energy Commission's 2025 Single-Family Residential Compliance Manual explains how replacement windows are treated, in its chapter on additions, alterations and repairs (Compliance Manual, Chapter 9) ⁷:

• Replacing windows across the house (prescriptive path). In one of the manual's worked examples, replacement windows, equal to or smaller than the existing window area in each wall, must meet a U-factor of 0.30 in climate zones 6 to 10 and 15, or 0.27 in climate zones 1 to 5, 11 to 14 and 16, and an SHGC of 0.23 in climate zones 2, 4 and 6 to 15 ⁷.
• Smaller replacements. Another worked example says up to 75 square feet of vertical replacement window area may meet a U-factor of 0.40 in all climate zones and an SHGC of 0.35 in climate zones 2, 4 and 6 to 15 ⁷.
• A mandatory ceiling. The manual refers to a mandatory maximum window U-factor of 0.40 ⁷.

The details, exceptions and the performance path (which trades better windows against other features of the house) are in the manual. In practice, ask each installer which Title 24 values the quoted window meets, and which climate zone they used.

California's 16 Title 24 climate zones are not the same as ENERGY STAR's four zones. The Title 24 values come from the state Energy Code (California Energy Commission); ENERGY STAR is a separate, voluntary label ⁵⁸.

ENERGY STAR climate zones in California

ENERGY STAR's county list places California counties in all four of its zones (ENERGY STAR climate zone finder) ⁹:

ENERGY STAR's list puts 39 of California's 58 counties in the South-Central zone, including the large coastal and Central Valley population centers ⁹. The Northern zone also offers equivalent options at slightly higher U-factors paired with higher SHGC ⁸. All four zones share an air leakage limit of 0.3 cubic feet per minute per square foot ⁸.

The energy-efficient windows explainer explains U-factor and SHGC in more depth.

Cost and next steps

California prices follow the same drivers as anywhere, plus the Title 24 glass requirements and any permit your city applies. This page does not quote California or city prices, because the national surveys do not publish reliable local figures. The window replacement cost guide sets the national surveys side by side, and how to choose a window installer covers the vetting beyond the license check. California cities handle window permits differently; the article on window replacement permits shows two California examples.

When you are ready, you can compare quotes from window installers.

About these figures

• ¹ Official record: CSLB release on AB 2622 (threshold raised from $500 to $1,000 effective January 1, 2025, conditions, advertising rule, penalties up to $15,000 and $5,000, six months, and the 10 percent down payment guidance), checked October 22, 2026.
• ² Official record: CSLB descriptions of the C-17 Glazing and Class B General Building classifications, checked October 22, 2026.
• ³ Official record: CSLB consumer page on hiring a contractor, linking the license check, checked October 22, 2026.
• ⁴ Official record: CSLB license and Home Improvement Salesperson lookup, checked October 22, 2026.
• ⁵ Official record: California Energy Commission Title 24 page (standards updated every three years), checked October 22, 2026.
• ⁶ Official record: California Energy Commission 2025 standards page (applies to permit applications filed on or after January 1, 2026), checked October 22, 2026.
• ⁷ Official record: 2025 Single-Family Residential Compliance Manual, Chapter 9 (replacement window U-factor 0.30 or 0.27 and SHGC 0.23 by climate zone, the 75 square foot replacement case at 0.40 and 0.35, and the 0.40 mandatory maximum), checked October 22, 2026.
• ⁸ Official record: ENERGY STAR Version 7.0 window criteria for all four zones (including air leakage 0.3), checked October 22, 2026.
• ⁹ Official record: ENERGY STAR county climate zone list for California (39 of 58 counties South-Central, Imperial Southern, and the counties named), checked October 22, 2026.