The date that matters is the permit application date. Submit on or after January 1, 2026 and you are under the 2025 Building Energy Efficiency Standards, full stop — it does not matter when the plans were drawn or when construction starts. Plenty of projects designed comfortably under the 2022 code are now discovering, at plan check, that the ground moved under them. Here is where it moved.

The performance run now has four hurdles, not three

A 2022-cycle performance run passed on three metrics: efficiency EDR, total EDR (which lets PV and batteries help), and source energy. The 2025 code adds a fourth check on peak cooling. In climate zone 4 and zones 8 through 15, the proposed design's space-cooling energy is capped at 120 percent of the standard design's.

Why does this matter? Because the old escape hatch is gone. Under the 2022 rules you could pair a mediocre envelope with a big PV array and the total-EDR metric would forgive a lot. The cooling cap is checked on its own, and solar panels do not shrink a cooling load. West-facing glass in Fresno now has to answer for itself.

Heat pumps in the baseline, everywhere

The 2022 code put a heat pump in the standard design for either space heating or water heating depending on climate zone. The 2025 code stops splitting the difference: the baseline building now has heat-pump space heating and heat-pump water heating in all sixteen climate zones. Gas is still legal. But a gas furnace or tankless is now compared against a heat pump it has to out-model, and it starts the run in a hole. On most new single-family work the cheapest compliance strategy is to just specify the heat pumps and spend your effort elsewhere.

QII is no longer a credit — it is the assumption

Quality Insulation Installation used to be the workhorse credit: pay for the third-party insulation inspection, collect a meaningful margin in the model. The 2025 code moved QII into the standard design for new construction. Same field work, opposite arithmetic. A project that includes QII gains nothing over the baseline; a project that skips it takes a penalty that is genuinely hard to make up. Put the verification in the budget from day one.

Windows: 0.27 and 0.30 are both right

The prescriptive fenestration requirement split. Smaller windows are held to a maximum U-factor of 0.27; larger units get 0.30, an acknowledgment that big glazing assemblies can't hit ultra-low U-factors at reasonable cost. If your spec still says “U-0.30 throughout” from the last cycle, check the schedule against both limits before the order goes in. Performance projects feel this too, because the standard design inherits the new values.

HERS is now called ECC

The rating infrastructure — raters, registries, field-verified forms — carries on under the name Energy Code Compliance. Your rater is probably the same person. The forms and the plan-check comments will say ECC where they used to say HERS, and it saves a confused phone call to know the rename happened on purpose.

The short version

  • Heat pumps for space and water heating unless something forces gas.
  • QII is a cost of doing business now, not a credit to trade.
  • In CZ4 and CZ8–15, get the cooling load right early — orientation, shading, glass area. PV won't save it.
  • Window schedules need checking against both U-factor limits.

A decent envelope with all-electric equipment tends to clear the 2025 code without drama. The projects that struggle are the ones that used to lean on credits and a big array. Enforcement details vary by jurisdiction, as always — when in doubt, ask your plan checker early rather than late.