How the 2025 Title 24 Calculation Differs From 2022: LSC, Heat Pump Baseline and Testing
The 2025 performance budget is set in long-term system cost (LSC) and source energy, and the standard design now assumes a heat pump. Prescriptive window U-factors, wall insulation minimums, refrigerant charge verification and PV sizing also moved, so a design that passed under 2022 should be re-run, not reused.
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The engine now scores differently
For a new single-family home the energy budget is expressed in source energy and LSC, and the compliance manual says the budget uses LSC instead of Time Dependent Valuation energy (Section 150.1(b)1). Additions and alterations are judged on LSC alone, not on the source energy test that applies to newly constructed buildings. The manual calls the single fuel baseline, with a heat pump prescribed for water heating and space heating, the most significant 2025 change for houses.
Six changes that move a result
- Heating baseline. The prescriptive package requires a heat pump in every climate zone, or the building must pass on performance (Section 150.1(c)6).
- Charge verification. Refrigerant charge verification is now required for heat pumps in all climate zones, and fault indicator displays no longer count as a verification method (Section 150.1(c)7A).
- Windows. The prescriptive maximum U-factor is 0.27 in climate zones 1 to 5, 11 to 14 and 16, and 0.30 elsewhere, except that a new dwelling of 500 square feet or less in zone 5 may use 0.30 (Table 150.1-A). Mandatory fenestration U-factor is a weighted average of 0.40 (Section 150.0(q)).
- Walls. Mandatory walls must reach an assembly U-0.095 in 2x4 framing and U-0.069 in 2x6, which the manual describes as a rise from R-13 to R-15 and from R-20 to R-21 (Section 150.0(c)).
- Cathedral ceilings. A new Option C allows R-38 across all climate zones (Section 150.1(c)1A).
- Solar size. PV is the smaller of the equation result or the solar access roof area times 18 for steep slopes or 14 for low slopes (Section 150.1(c)14).
What stayed put
There are still two routes after the mandatory floor, performance or prescriptive, and compliance software may not check the mandatory measures for you. See the prescriptive versus performance comparison.
What it means for an older design
Re-run the numbers on 2025 software, confirm the equipment type and re-check glass values by climate zone. The headline changes and the edition date rule give the background, and a permit started under 2022 keeps its edition. For a new design, order a residential report.
Common Title 24 Questions
- What is Title 24?
- Do I need a Title 24 report?
- How much does a Title 24 report cost?
- How long does a Title 24 report take?
- What is included in a Title 24 report?
- What plans do I need to upload?
Frequently Asked Questions
Not necessarily. The manual warns that compliance software may not automatically check the mandatory measures, so the plans still need a mandatory-measures check.
No. The direction depends on your equipment, windows and climate zone. A heat pump home with efficient glass may score well, while a gas furnace design loses ground to the new baseline.
Explore 2025 Energy Code and 2026 Permits
- Title 24 Hotline: Who to Ask About an Energy Code Question
- Does My Project Fall Under the 2022 or the 2025 Energy Code?
- Will the Energy Code Change Again? The 2028 Title 24 Code and What It Means for a 2026 Permit
- Title 24 Requirements in California
- What Changed in the 2025 Energy Code?
View all 2025 Energy Code and 2026 Permits guides → · Title 24 Guide · Title 24 guide