Is Solar Required on a New Home in California?
Usually yes for newly constructed homes — but the required size is the smaller of a calculation from climate zone, floor area and dwelling unit count and a figure set by your Solar Access Roof Area. If that works out below 1.8 kWdc, no system is required.
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Two methods, and the smaller one wins
The minimum system size is determined two ways, and the requirement is whichever produces the smaller answer:
- the building's Solar Access Roof Area — the roof area actually available and suitable for panels — multiplied by 18 for a steep-sloped roof or 14 for a low-sloped roof
- Equation 150.1-C, driven by climate zone, conditioned floor area and the number of dwelling units
Taking the smaller is what makes the requirement buildable. A house with a small, shaded or awkward roof is not asked to install a system it has nowhere to put — the roof caps the obligation. On a steep roof, the parts facing roughly north (between 300 and 90 degrees from true north) do not count, and if less than 80 contiguous square feet of usable roof is left, no system is required.
The 1.8 kWdc floor
Where the calculated minimum comes to less than 1.8 kWdc, no PV system is required at all.
This is the exemption that resolves small projects. A very small dwelling, or one whose usable roof area is minimal, can calculate out below the threshold and owe nothing. It is a real outcome rather than a technicality, and it is worth calculating rather than assuming either way.
Why climate zone changes the answer
Equation 150.1-C takes the climate zone as an input because both the electrical load and the solar resource vary across California. A house in a hot inland zone has a larger cooling load and more sun; a coastal zone has less of both. The same floor plan therefore carries different obligations in different places — which is consistent with how the rest of the Energy Code treats zones.
Conditioned floor area, and unit count
Floor area drives the calculation because it stands in for load. Dwelling unit count is separate: a duplex is not simply a larger house, and the equation accounts for the unit count rather than only the total area.
Solar Access Roof Area is a design variable
Because SARA caps the requirement, roof design directly affects it. Orientation, pitch, shading, and how much of the roof is consumed by vents, flues and equipment all reduce the area available. That is a coupling worth knowing at design stage: the roof plan is part of the energy compliance answer, not just an architectural decision.
A battery reduces the requirement
The size from Equation 150.1-C may be reduced by 25 per cent when the system is installed with a battery that meets Joint Appendix JA12 and has at least 7.5 kWh of cycling capacity. See JA12 battery storage requirements.
What this is not
This is the single-family requirement. Low-rise multifamily and nonresidential buildings have their own PV provisions with different triggers and different sizing — a nonresidential building is sized in watts per square foot of roof by slope, and also carries a battery storage requirement. Do not carry an answer across between them.
Common Title 24 Questions
- When is Title 24 required for a home?
- Does a remodel need Title 24?
- Does a room addition need Title 24?
- What plans are needed for a residential Title 24 report?
- How much does a residential Title 24 report cost?
- How long does a residential Title 24 report take?
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