What this code requires
Title 24 Part 6 Section 150.1(c) requires every new low-rise residential building in California to include a solar photovoltaic system sized to the building's energy use. The system capacity is calculated using a formula that accounts for conditioned floor area and climate zone — the plan set must either show a code-compliant PV system or document an approved exception. Single-family homes and ADUs fall under this requirement for permits applied for on or after January 1, 2026, under the 2025 Title 24 standards. Multifamily buildings up to three habitable stories have a parallel PV requirement in Section 170.2(f).
How to fix it
Confirm your climate zone and pull the correct sizing table
Before touching the drawings, confirm which 2025 Title 24 climate zone your project sits in — look it up on the CEC climate zone map at energy.ca.gov if you're not sure. The required PV capacity is calculated with Equation 150.1-C: kWPV = (CFA x A) / 1000 + (NDU x B), where CFA is conditioned floor area in square feet, NDU is the number of dwelling units, and A and B are the per-climate-zone adjustment factors from Table 150.1-C in the 2025 standards. Each climate zone has its own A and B factors. Run the calculation in a spreadsheet and verify you're using the 2025 table, not an older cycle's.
Show the PV sizing calculation on the energy compliance sheets
Put a clearly labeled calculation block on your Title 24 energy sheets — typically on the CF1R compliance form or the energy section of your cover sheet. Show the conditioned floor area input, climate zone number, the A factor you're applying, and the resulting required kWdc. Then show the proposed system capacity alongside it so the plan-checker can do a direct comparison. A note saying 'solar per Title 24' without numbers will not close the correction. The plan-checker needs to see the math, not just a statement that you did it.
Add the PV system to the electrical one-line diagram
Your electrical sheets need a one-line diagram showing the PV array, the inverter or microinverters, the AC disconnect, the interconnection point at the main panel, and the system's rated capacity in kWdc. Call out the number of panels, watt-class per panel, and total array output. If you're using microinverters, note the output per unit and the total. The rated capacity on the one-line must match the sizing calculation on the energy sheets — any discrepancy between the two will pull a second round of corrections.
Draw the roof plan showing panel placement and fire access pathways
Show panel location, orientation, and tilt on a scaled roof plan. Mark the required access pathways: at least two 36-inch pathways from the lowest roof edge to the ridge, and an 18-inch or 36-inch clear setback at the ridge depending on array coverage (CRC R329.6), though local AHJs sometimes require more. Label the number of panels per array string and show any roof obstructions (HVAC equipment, skylights, chimneys). If obstructions reduce usable area, your sizing calculation needs to account for them. If you still have enough unshaded area after setbacks, call that out explicitly on the plan so the plan-checker doesn't have to guess.
Document any approved exception with required supporting materials
If you're claiming an exception, cite the specific exception number from Section 150.1(c)14 in your note block and attach the required backup. The exceptions cover a steep-slope solar access roof area (SARA) under 80 contiguous square feet, a calculated system under 1.8 kWdc, roof designs the building department finds cannot meet ASCE 7-16 snow loads, and certain planning approvals from before January 1, 2020; a qualifying battery can also cut the required size by 25 percent. For limited roof area, attach a shading analysis showing which areas fall below 70 percent annual solar access. Put the exception documentation in your submittal package and reference it by sheet number from the energy compliance sheet. A verbal description of the problem without the required backup will come back as an incomplete correction.
Update the CF1R to include the PV system output
The CF1R compliance certificate needs to include the PV system in the energy budget calculation. If you're using CBECC-Res or another Title 24 compliance tool, enter the PV system parameters and re-run the simulation so the CF1R output shows the system. A CF1R generated before you added the PV system will be missing that data, and the plan-checker will flag it. Resubmit the updated CF1R with your correction response package. If your energy consultant generated the original CF1R, loop them in — they'll need to update the model file and reissue the compliance document.
For multi-unit projects, add a per-unit capacity allocation schedule
If the project has two or more dwelling units, prepare a schedule showing each unit's conditioned floor area, its required PV capacity per the 150.1(c) formula, and how that capacity is provided by the proposed system. If a single shared rooftop array serves all units, show the output allocation in the schedule. The plan-checker needs to trace from each unit's floor area through the formula to a specific portion of the proposed array. Missing this schedule is one of the top reasons multi-unit projects get a second 150.1(c) correction after the designer thought they'd addressed the first one.
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Why you got flagged
Plan-checkers flag 150.1(c) for a handful of consistent reasons. Here are the most common.
The most frequent trigger is a PV system that simply isn't shown on the plans at all. If your electrical or site sheets don't include a one-line diagram, a roof plan showing panel placement, and a calculation showing the system kWdc capacity matches or exceeds the code-required minimum, the plan-checker has no way to verify compliance. The correction will ask you to add those drawings and the sizing calculation before they'll move forward.
A second common flag is an undersized system. The 150.1(c) formula ties required capacity to conditioned floor area, with a per-climate-zone adjustment factor. If your calculation used the wrong climate zone, applied an outdated formula from a prior code cycle, or just math-errored the square footage input, the resulting kWdc will come out short. Plan-checkers run the math themselves, and a system that's even a fraction of a kWdc under the minimum fails the check.
Missing or improperly documented exceptions are the third scenario. 150.1(c)14 does list recognized exceptions, such as too little unshaded roof area, a calculated system under 1.8 kWdc, snow-load limits, and certain pre-2020 planning approvals. But an exception doesn't just get noted on the cover sheet. You need to show the specific exception number, supporting documentation (shading analysis, roof area takeoff, or the approval that applies), and a clear path for the plan-checker to close it. A general note saying 'tree shading — PV not feasible' won't close the correction.
Multi-unit projects sometimes get flagged because the designer calculated a single system for the whole building but didn't assign the capacity allocation correctly across units. Each dwelling unit's share of the PV system output needs to be traceable back to that unit's conditioned floor area. If the schedule doesn't map capacity to units, expect a correction asking for that breakdown.
The official code
California Energy Commission — Title 24 Part 6 Building Energy Efficiency Standards, Section 150.1(c)14 Photovoltaic Requirements
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