Field notes / Homeowner guide
California's 2025 Energy Code and a new custom home
The 2025 Building Energy Efficiency Standards took effect on January 1, 2026. Which edition a house must meet depends on when the building permit application was submitted, so the date matters for design and equipment.
Written · Revised · KB Remodeling
In brief
Confirm the permit application date, ask your designer which code edition and compliance software apply, and decide equipment early.
01
Which edition applies
The California Energy Commission states that buildings whose permit applications are applied for on or after January 1, 2026 must comply with the 2025 Energy Code. The Building Standards Commission's Bulletin 25-01 states the 2022 code still applies where the building permit application was received on or before December 31, 2025.
Cities can set their own rules on what counts as a complete application. Hermosa Beach, for example, says a project vests when a complete application and plan submittal are received, not at planning approval.
Ask yourself
- When was, or will be, the permit application submitted?
- What does the city count as complete?
02
What the 2025 code emphasizes
The CEC summarizes the 2025 Energy Code as expanding heat pumps in new residential buildings, encouraging electric-readiness and strengthening ventilation standards. Its overview also notes that the HERS program moves to Title 24, Part 1 and is renamed the Energy Code Compliance program.
These choices affect mechanical design, electrical capacity and sometimes the utility service, so they belong early in design and in the budget.
Ask yourself
- Which space and water heating approach is planned?
- Does electrical service size need to change?
03
Compliance documents
Compliance is shown with CEC-approved software and documents for the applicable edition; the CEC overview states 2025 projects must use 2025 software and compliance documents. The CEC also publishes a 2025 Single-Family Residential Compliance Manual.
Ask yourself
- Who prepares energy compliance documents?
- Which field verification will be needed?
04
Budget and schedule effects
Energy compliance appears in the budget as design, equipment, field verification and possible electrical work. In the schedule it appears in design and plan check. Ask your team for these lines rather than assuming a number.
Ask yourself
- Where do energy items appear in the estimate?
05 · The decision
Mandatory, optional and still in rulemaking
Keep three categories apart in your design notes. Mandatory: the 2025 Building Energy Efficiency Standards apply to permit applications submitted on or after January 1, 2026, as the California Energy Commission states (read October 13, 2026). Options: within the compliance approach your designer chooses, some envelope, equipment and system choices trade against each other. Future rulemaking: the Commission already publishes a page for the 2028 standards; treat it as a development to watch, not a rule your 2026 application must meet.
The decisions an owner coordinates are envelope (insulation, windows, air sealing), heating and cooling (the 2025 edition expands heat pump use in new homes), ventilation (strengthened in this edition), electric-readiness for future equipment, and solar and battery storage where the standards call for them. The Commission issued corrections to the battery storage capacity requirements on June 9, 2025, which is a reminder to rely on the current official documents rather than summaries. Sizing, ratings and system selection are for the energy consultant and engineer, not this guide.
| Decision | Prepared by | Document | Hands off to |
|---|---|---|---|
| Compliance approach | Energy consultant or designer | Compliance documents for the application | Building department plan check |
| Envelope | Architect with energy consultant | Assemblies and window schedule on drawings | Builder for pricing |
| Heating, cooling, ventilation | Mechanical designer or engineer | Equipment and ventilation design | Builder; electrical load to the utility application |
| Electric-readiness | Electrical designer | Panel and circuit provisions on drawings | Utility service application |
| Solar and storage | Designer per the standards | System scope where required | Utility interconnection process |
Ask yourself
- Which compliance approach is the designer using, and what does it trade off?
- Which choices are mandatory for this application versus options the team is proposing?
- Who confirms the current official documents, including any corrections, before submittal?
06 · When it applies
Planning work in 2027: what is in effect, what is scheduled and what has ended
Sources read October 13, 2026. In effect: the California Energy Commission states that buildings whose permit applications are applied for on or after January 1, 2026 must comply with the 2025 Energy Code, and the Building Standards Commission describes the 2025 California Building Standards Code as published July 1, 2025 and effective January 1, 2026. An application filed in 2027 would, on that basis, fall under the 2025 edition unless a later edition takes effect first; confirm the edition with your authority at filing.
Scheduled, not adopted: the Commission's 2028 Energy Code page says the updated standards will be proposed for adoption in 2027 with an effective date of January 1, 2029. Until adopted, their content is unknown and nothing in them applies to your project.
Ended: IRS instructions for Form 5695 state that residential clean energy credits cannot be claimed for expenditures made after December 31, 2025, and energy efficient home improvement credits cannot be claimed for property placed in service after that date. Do not budget 2027 work around those federal credits. Utility or local programs have their own, changing terms; check the program's current page before relying on any of them. This is not tax advice.
| Development | Status | Effective / end date | What it means for an owner |
|---|---|---|---|
| 2025 Energy Code and 2025 Title 24 | In effect | Applications on or after Jan 1, 2026 | Expect this edition for 2027 filings unless a later one takes effect |
| 2028 Energy Code | Announced schedule; proposed for adoption in 2027 | Jan 1, 2029 (announced) | Watch; no requirements yet |
| Federal residential clean energy and home improvement credits | Terminated | After Dec 31, 2025 | Not available for 2027 work |
Ask yourself
- Which code edition will our authority apply on the date we file?
- Are we relying on any incentive, and what do its current terms say?
A scenario to consider
Illustrative scenario, not a client project: an owner's design was started in 2025 but the permit application is submitted in February 2026. The designer reruns compliance under the 2025 code before submittal.
Planning scenario
Part of the custom-home planning series: Custom home planning
Bring this to your conversation
- Record the permit application date
- Ask which code edition applies
- Decide heating and water-heating equipment early
- Check electrical service capacity
- Ask who prepares compliance documents
Terms used here
- Plan check
- Agency examination of submitted construction documents; the reviewer may request corrections before approval.
One more question
My design started in 2025. Which energy code applies?
Generally the edition in effect when the building permit application is submitted. Applications submitted on or after January 1, 2026 use the 2025 code; confirm with your building department.
Official references
Prepare plans and ADUs · Web resource · English source
California Energy Commission — 2025 Building Energy Efficiency StandardsUse this for: Find the 2025 energy standards and discuss the applicable compliance path with the design team.
Prepare plans and ADUs · PDF · English source
California Energy Commission — 2025 Energy Code OverviewUse this for: Orient an energy-design conversation using the dated 2025 overview.
Prepare plans and ADUs · PDF · English source
California Building Standards Commission — Information Bulletin 25-01 (July 1, 2025)Use this for: Discuss the code-cycle bulletin and application timing with the reviewing office.
Prepare plans and ADUs · Web resource · English source
California Energy Commission — 2028 Energy Code timelineUse this for: Follow the announced 2028 Energy Code schedule; nothing there applies until adopted and effective.
Prepare plans and ADUs · PDF · English source
IRS — Form 5695 instructions (credit termination)Use this for: Check the IRS status of federal residential energy credits before budgeting for them.
For requirements specific to your property, consult the local reviewing authority.
About this guide
Published by KB Remodeling from the official sources cited. It is not attributed to an individual author and does not claim review by an architect, engineer or attorney. We receive remodel, ADU, new-home and rebuild inquiries; scope, licensing and location are reviewed before any next step.