§150.1(c)14 · Solar PV mandate

# §150.1(c)14: Solar PV mandate

What it requires

Newly constructed low-rise residential buildings must install a solar PV system sized by floor area and dwelling-unit count, per the formula:

> kWdc = (CFA × CFAmult / 1000) + (NDU × DUmult)

Where:

• CFA = conditioned floor area (ft²)
• NDU = number of dwelling units (2 when an ADU is on the project, else 1)
• CFAmult and DUmult are climate-zone-specific factors from CEC's T24RClimateZoneCodeBaselines.csv

The required kW lands on the CF1R and is what your contractor uses when sizing the array.

When it applies

• Newly constructed single-family homes. Required.
• Newly constructed detached ADUs. Required, the 2025 ADU FAQ classifies a detached ADU as new construction.
• Newly constructed low-rise multifamily (in scope but not yet supported by our service).

When it does NOT apply

• Additions to existing residences. §150.2(a) excludes them.
• Alterations. §150.2(b) excludes them.
• Attached ADUs. Classified as additions to the existing house, not new construction.
• Add-Alone with attached or non-ADU addition. Same as additions.

See §150.2(a), additions for the scope definition and §150.2(a) exception 2 for the small- project carve-out.

How we use it

When your project's scope triggers the mandate, we compute the required kW automatically from the floor area and dwelling-unit count you confirm. The value lands on the CF1R; we don't sell or install panels, your contractor uses the kW value to size the system. See the PV mandate decoded article for the full breakdown.

Common gotchas

• ADU + main-house projects: the NDU value flips to 2, which roughly doubles the per-unit additive on the PV sizing formula. Easy to miss when the architect drew the ADU as part of the main-house package.
• Detached ADU classification, if the breezeway connecting the ADU to the main house is over a threshold, the ADU is "attached" and PV is exempt. The threshold trips up plan-checkers regularly.
• "Newly constructed" carve-outs for Live-Work units, they don't apply to ADUs but do apply to mixed-use cases out of scope of residential Title 24.