ADU Questions · 2026
Do ADUs Require Solar Panels in California?
In most cases, yes. If you’re building a newly constructed, detached ADU and your permit application was submitted on or after January 1, 2020, California’s Title 24 energy code generally requires solar panels, the same way it does for new single-family homes. But several common exemptions can remove that requirement entirely, depending on your ADU’s size, your climate zone, and your roof.
The short version: New detached ADUs generally need solar under Title 24. Attached ADUs and conversions (garage, basement, attic, or built inside the existing home’s footprint) are usually exempt because they’re treated as alterations, not new construction. Some smaller detached ADUs also qualify for a small-ADU exemption, and a limited-solar-access exemption applies when the roof simply doesn’t get enough usable sun. The exact answer for your project depends on specifics that only your plan set can confirm.
Why solar shows up on ADU plans at all
Title 24 is California’s statewide building energy efficiency code. Since 2020, it has required most new residential construction, including detached ADUs, to include a solar photovoltaic system sized to the home. The idea is straightforward: a brand-new detached structure is treated like any other new dwelling, so it gets the same energy standards as a newly built single-family house.
That’s why, if you’re planning a standalone backyard ADU on a new foundation, your architect or engineer will likely calculate a solar requirement as part of the plan set, right alongside insulation, window ratings, and HVAC specs.
The three situations where solar isn’t required
Not every ADU triggers the solar requirement. Three exemptions come up most often:
| Exemption | When it applies |
|---|---|
| Small-ADU exemption | When the calculated solar requirement for the unit works out to be very low, smaller detached ADUs can end up exempt in practice. Whether yours qualifies depends on your specific size and climate zone calculation. |
| Limited-solar-access exemption | If very little of the usable roof area gets adequate sun (heavy shading from trees, neighboring structures, or roof orientation), the project can qualify for this exemption. |
| Attached ADU or conversion exemption | Attached ADUs and conversions, meaning a garage, basement, or attic conversion, or any ADU built within the existing home’s footprint, are treated as alterations rather than new construction. These generally are not subject to the new-construction solar requirement at all. |
If your ADU is a garage conversion, for example, you’re very likely in the clear on solar. Our guide to garage conversions to ADUs walks through how that conversion path works more broadly.
How to know your specific answer
Because the solar requirement is a calculation, not a flat rule, the honest answer to “does my ADU need solar” is: it depends on your model’s size, your city’s climate zone, and your roof’s sun exposure. Two nearly identical ADUs built a few miles apart, in different climate zones or with different roof shading, can land on opposite sides of the requirement.
That’s not a dodge, it’s how the code is actually written. The reliable way to get a real answer is to have it calculated as part of your plan set, where an engineer runs the actual Title 24 numbers for your specific address, model, and roof. Guessing based on a neighbor’s project or a general rule of thumb isn’t a safe substitute.
How this fits into building with Framework First
Every Framework First ADU is fully permitted before it ever leaves the Salinas factory, and that includes energy compliance. Title 24 solar, when it applies, gets calculated and built into your plan set and into your project price as part of our all-inclusive process, which is built around a permitting budget along with foundation, delivery, utility hookups, and final inspection, with exact permit costs confirmed for your address in the feasibility study. You’re not left to figure out solar requirements on your own after the fact.
If you’re comparing models and want to see how detached versus attached configurations affect a project, browse our ADU models or start with a feasibility study to get answers specific to your lot, your city, and your roof. You can also read more on how California’s ADU rules work overall in our guide to California ADU laws in 2026.
Frequently asked questions
Does a garage conversion ADU need solar panels?
Generally, no. A garage conversion is treated as an alteration to an existing structure rather than new construction, so it typically falls outside the Title 24 solar requirement that applies to newly built detached ADUs. Confirm this with your specific plan set, since local conditions can vary.
Is there a size cutoff where small ADUs are exempt from solar?
There’s a small-ADU exemption that can apply when the calculated solar requirement for the unit is very low, which in practice often ends up exempting smaller detached ADUs. Whether your specific model qualifies depends on its size, your climate zone, and the calculation your engineer runs, so it’s not a fixed square-footage cutoff you can apply on your own.
What if my roof doesn’t get much sun?
There’s a limited-solar-access exemption for situations where very little of the usable roof area receives adequate sunlight, often due to shading from trees or nearby structures. If your roof qualifies, the solar requirement can be waived even for a new detached ADU.
Does an attached ADU need solar panels?
Usually not. Attached ADUs are generally treated as alterations to the existing home rather than new construction, which typically places them outside the Title 24 new-construction solar requirement. As always, your plan set is the definitive source for your specific project.
Who determines whether my ADU needs solar?
Your plan set does. A qualified engineer or your builder’s plan-review process runs the actual Title 24 calculation based on your model’s size, your city’s climate zone, and your roof’s real sun exposure. That calculation, not a general rule, is what determines your final answer.
Ready to find out exactly what applies to your property? Start a feasibility study or browse Framework First’s ADU models to get specifics for your lot.