ASHRAE 90.1 vs California Title 24: What Contractors Need to Know
If you bid work in more than one state, you eventually hit the question: which energy code actually applies, and how different are they? For lighting and lighting controls, the two names that matter most are ASHRAE 90.1 and California's Title 24, Part 6. They overlap a lot, but they are not the same document, and a controls package that passes in one place can fail plan review in another. Here's the practical breakdown.
The short version
- ASHRAE 90.1 is a national model energy standard. States adopt it (or the IECC, which references much of the same lighting content) as the basis for their commercial energy code.
- Title 24, Part 6 is California's own mandatory energy code. It is written and enforced by the California Energy Commission, not adopted from ASHRAE.
- Title 24 is generally the stricter of the two, especially on lighting controls and acceptance testing. If you build to Title 24, you will typically meet or exceed ASHRAE 90.1.
Which code applies to your project
Outside California, your project most likely follows whatever your state has adopted, which is usually a version of the IECC, ASHRAE 90.1, or both. Under federal energy law, each state's commercial code is measured against the latest published ASHRAE 90.1 (currently the 2022 edition), and states certify whether their code is at least as efficient. The result is a patchwork: different states are on different editions, ranging from older cycles up to 90.1-2022. The U.S. Department of Energy tracks current adoption state by state at energycodes.gov.
In California, the answer is simpler: Title 24, Part 6 applies, and it is mandatory. It is not interchangeable with ASHRAE 90.1 or the IECC. The current cycle is the 2025 Energy Code, which applies to building permit applications submitted on or after January 1, 2026.
Where the lighting-control rules line up
Recent editions of both codes have converged on the same core control strategies, so the types of controls you install look similar:
- Automatic shutoff when a space is vacated. Both ASHRAE 90.1-2022 and Title 24 require occupancy-based shutoff in many space types; for example, larger offices (roughly 300 sq ft and up under 90.1-2022) need occupancy sensors that shut lighting off within about 20 minutes of vacancy.
- Multilevel / dimming control so general lighting isn't just full-on or full-off.
- Daylight-responsive controls in daylit zones above a wattage threshold (commonly around 75 W of general lighting in a daylit area).
- Manual controls that let occupants turn lighting down or off.
So at the equipment level, occupancy sensors, daylight sensors, and 0-10V dimming show up in both. (For the products that satisfy these, see our commercial occupancy sensor buying guide.)
Where Title 24 goes further
The differences that trip up out-of-state teams are mostly about how strict and how verified Title 24 is:
- Lighting power allowances. Both codes cap lighting power, expressed as a lighting power density (LPD) that varies by space type and building. Title 24's allowances are generally tighter and its compliance accounting is more detailed. (Treat any blog claiming a single blanket "X watts per square foot" mandate skeptically; allowances are space-by-space, not one number.)
- Acceptance testing. This is the big one. Title 24 requires installed lighting controls to be functionally tested and certified by a qualified Acceptance Test Technician. ASHRAE 90.1-2022 also calls for acceptance testing of certain controls, such as daylight-responsive controls, but California's program is broader and more formalized. Systems that are installed but never programmed, tested, or documented can fail inspection even if the right hardware is on the wall.
- Demand response. Title 24 requires larger lighting systems to accept a demand-response signal using a qualifying OpenADR standard.
- Cost-effectiveness math. California uses different energy-cost and discount-rate assumptions, which pull more daylighting and control measures into the "required" column than a baseline 90.1 project would see.
The practical takeaway for multi-state contractors
Most teams that work across state lines don't try to bid two different control packages. They design one superset package that satisfies the strictest jurisdiction they work in, which in practice usually means designing to Title 24 and letting that carry the ASHRAE 90.1 and IECC jobs. The extra cost of the stricter sensors and dimming is usually small next to the risk of a failed plan review or a failed acceptance test.
Two things still need project-specific attention every time: the exact code edition your jurisdiction is on, and the acceptance-testing and documentation requirements, since that paperwork is where otherwise-compliant jobs get held up.
How Rock helps
Rock Lighting & Electric is an authorized Wattstopper / Legrand and Lutron dealer and distributor. We stock the occupancy sensors, daylight sensors, room controllers, and dimming controls that meet both ASHRAE 90.1 and California Title 24, at contractor pricing with nationwide shipping. Send us your plans or control schedule and we'll help you spec a package that holds to the stricter of the two codes. Start with the Wattstopper or Lutron collections, or contact us with your job details.
FAQ
Is Title 24 the same as ASHRAE 90.1?
Which energy code applies to my project?
Is ASHRAE 90.1 or Title 24 stricter for lighting?
Do both codes require acceptance testing?
Can I use the same lighting controls for ASHRAE 90.1 and Title 24 jobs?
This article is general guidance, not a substitute for the official code text or a licensed energy/Title 24 compliance professional. Confirm the adopted code edition and requirements for your specific occupancy and jurisdiction.