What the 2025 Energy Code changed, and who it catches out

The 2025 Energy Code took effect on January 1, 2026. If your permit application was filed on or after that date, it governs your project — regardless of when the design was produced.

The date rule, first

This is the single most expensive misunderstanding in California energy compliance. The applicable code cycle is set by the permit application date. Not the date the drawings were finished, not the date construction begins, not the date the report was commissioned. A project designed in 2025 but permitted in 2026 is a 2025-code project.

The consequence of getting it wrong is not a minor correction. A report modelled to the wrong cycle usually has to be rebuilt, and the design frequently needs changes to comply with the newer standard. That is weeks, not days.

Heat pumps moved into the baseline

The most consequential change. For newly constructed residential buildings, the standards expanded the use of heat pumps for both space and water heating — shifting them from an alternative you could choose into the assumption the baseline is built around. Gas equipment is not prohibited, but designs relying on it now have more compliance ground to make up elsewhere.

Electric-readiness expanded

Where gas equipment is installed, the building generally has to be ready for its electric replacement later: circuit capacity, panel space and physical clearance for future equipment. This is cheap to accommodate at design and expensive to retrofit, which is precisely why the requirement exists.

Ventilation strengthened

Ventilation requirements were reinforced across the standards. As envelopes get tighter, mechanical ventilation carries more of the indoor air quality burden, and the code has followed that logic.

Multifamily continues to diverge

Multifamily requirements have been separating from single-family across recent cycles, and the gap widened again. Teams that apply single-family assumptions to a low-rise multifamily project routinely produce a model that does not comply.

What to do about it

If you have a project in design now, confirm the anticipated permit application date and model to that cycle. If you have a report produced before the changeover and have not yet submitted, have it checked before you file — it is far cheaper than a rejection.

The California Energy Commission is already developing the 2028 standards, so this will happen again. Building the date check into your process is worth more than remembering it once.