# §150.1(c)14 Exception 2: Small-project PV exception
What it requires
Exception 2 to the §150.1(c)14 PV mandate carves out projects where the prescribed PV system is below 1.8 kWdc, typically because the conditioned floor area is small enough that the PV formula produces a number too small to install economically (the minimum system size for a residential PV install in California is around 1.8–2.0 kWdc).
The exception applies automatically; the Title 24 compliance analysis infers it from the prescribed-PV calculation. No manual flagging required.
When it applies
The most common scenario is a detached ADU under ~700 ft² in a climate zone with low PV factors (CZ1, CZ16, CZ6). Larger CFA or higher PV factors push the prescribed kW above the 1.8 kWdc threshold.
When it does NOT apply
- Additions and alterations, these don't trigger §150.1(c)14 at all (per §150.2(a)), so Exception 2 is irrelevant.
- Newly constructed single-family homes, too large for Exception 2 to kick in.
How we use it
When your project's prescribed PV is below the threshold, we set size_kw=0 on the CF1R and leave the §150.1(c)14 exception field at its default sentinel. The customer-facing copy on the design option card reads "PV not required, Exception 2 (small project)".
A compliance-engine quirk worth knowing: we do not set the ReducedPVReqExcept enum to (R Exc.2) even though the rule text implies we should. The current Title 24 ruleset rejects that enum with a code-43 parse error. Every saved reference compliance file emits the default sentinel even when no PV is being installed; the engine infers the exception internally from the prescribed-PV calculation. We follow the reference-file convention.