Every solar company that calls about a Sacramento-region ADU project says the same thing: yes, you need panels, it's the law. Every neighbor who built one two years ago without a single panel on the roof says something different. Both of them are telling the truth. They're just describing different ADUs.
California's solar requirement for new construction doesn't live where most homeowners expect it. It's not in CalGreen, the green building code people have usually heard of secondhand. It's in Title 24 Part 6, the energy code, the same part that sets insulation and window standards. And it doesn't apply the same way to every ADU. Whether your project triggers it depends on how the unit gets built, how big the state's formula says the required system needs to be, and how much usable roof you actually have. Get that wrong at the design stage and you're either paying for a system you didn't need or discovering a compliance gap at plan check, after the roof framing is already drawn.
This guide covers who's actually subject to the mandate across Sacramento, Davis, Elk Grove, Folsom, Woodland, West Sacramento, Roseville, and Dixon, where the real exemptions sit, what battery storage does and doesn't require, what solar adds to a 2026 ADU budget, and why none of these eight cities currently layers its own solar rule on top of the state's.
Quick Answer
New, site-built, detached ADUs are generally subject to Title 24 Part 6's solar PV sizing requirement, the same rule that applies to new single-family homes, just scaled to the ADU's own conditioned floor area and climate zone. Attached ADUs, garage conversions and other conversions of existing space, JADUs, and factory-built ADUs installed on a permanent foundation are generally treated as alterations, or regulated on a separate track entirely, and generally fall outside that new-construction PV requirement. Even among detached units that are subject to it, a small-ADU exemption kicks in when the calculated system size works out under roughly 1.8 kW, which in practice tends to land around detached units under approximately 600 to 700 square feet, depending on climate zone. A second exemption applies if the usable roof area is under about 80 contiguous square feet.
Where the mandate does apply, plan on $1,500–$4,000 for Title 24 energy compliance documentation and, separately, roughly $4,500–$12,000 for the physical PV system itself on a typical mid-size detached unit, based on 2026 California-wide solar pricing. None of the eight cities in this cluster currently stacks a local solar rule on top of the state formula, and state law just made that harder to change: AB 130 froze new local residential building standards statewide from October 1, 2025 through June 1, 2031.
Not sure whether your specific floor plan crosses the exemption line? That one's a code question, not a pricing question, so call us at (530) 204-8294 and we'll walk through which category your ADU falls into before you finalize a design. Once you know that, SafewayQuickQuote.com will give you a cost ballpark for the build itself in about two minutes.
Title 24 Part 6, Not CalGreen: Clearing Up the Confusion
Title 24 is the umbrella term for California's building standards code, and it has multiple parts covering completely different things. Part 11 is CalGreen, the California Green Building Standards Code, and it deals with water efficiency, construction waste diversion, EV charging infrastructure, and material standards like low-VOC finishes. Part 6 is the energy code, covering insulation values, window performance, HVAC efficiency, and, since it was extended to more building types in the 2022 code cycle, solar PV sizing for new construction.
The solar mandate is a Part 6 rule, not a CalGreen measure. It shows up in the same conversation as CalGreen because both parts get reviewed together at plan check, and a new detached ADU is exactly the kind of project where both matter at once, waste diversion documentation from Part 11, solar sizing from Part 6. That overlap is where the confusion usually starts. Keep the two straight and a lot of the “does my ADU need solar” question answers itself once you know which code section you're actually asking about.
As of this writing, the applicable version is the 2025 Energy Code, which governs permit applications submitted on or after January 1, 2026, meaning it's the active standard for any Sacramento-region ADU permit going in right now.
Want to know how this interacts with the rest of your ADU's design and permitting? Call us at (530) 204-8294 or start with a free estimate at SafewayQuickQuote.com.
Who Actually Triggers the Mandate
This is the question that decides everything else, and it's not a square-footage rule on its own.
Subject to it: new, site-built, detached ADUs. A freestanding backyard unit, built from a new foundation up, is classified as new construction under Part 6, the same category a brand-new single-family home falls into. That's the project type the solar sizing formula was written for.
Generally exempt: attached ADUs. An ADU built as an addition onto the existing house, sharing a wall or a roofline with the primary structure, is generally treated as an addition to an existing building rather than new construction. Additions to existing, already-conditioned homes generally aren't pulled into the new-construction PV requirement the same way a detached unit is.
Generally exempt: garage conversions and other interior conversions. Converting an existing garage, basement, or other conditioned or unconditioned space into an ADU is generally treated as an alteration under Title 24, not new construction, so the standard solar mandate generally doesn't reach it. This is a genuine cost advantage of the conversion path worth weighing against a from-scratch detached build; we cover the fuller tradeoff in our Sacramento garage conversion ADU guide.
Generally exempt: JADUs. A junior ADU has to be built within the existing walls of the primary home by law, which keeps it out of the new-construction category entirely.
Regulated separately: factory-built ADUs. A modular or factory-built ADU installed on a permanent foundation is generally regulated on its own track under state factory-built housing standards, distinct from the site-built new-construction path the standard PV formula was written for.
None of this is a loophole to game. It's simply how the code defines “new construction” versus “alteration,” and the definition happens to track fairly closely with which ADU types actually get a from-scratch roof, walls, and foundation versus which ones reuse something that's already there.
The Small-ADU Exemption: The Real Number
Even a new, site-built, detached ADU isn't automatically on the hook. Title 24 Part 6 sizes the required system using a state formula, commonly referenced across industry sources as Equation 150.1-C, that factors in the ADU's conditioned floor area and its climate zone. Run that calculation for a genuinely small unit and the required system size can come out below the threshold where a system is mandated at all.
That threshold sits at roughly 1.8 kW. If the calculated requirement lands under that number, the small-ADU exemption applies, and no solar installation is required. In practice, that tends to correspond to detached ADUs somewhere under approximately 600 to 700 square feet, though the exact break point moves with your specific climate zone and, to a lesser degree, roof orientation, so don't treat 650 square feet as a hard universal line for your address.
A second, separate exemption exists for limited solar access. If the roof's usable, unshaded area, the space that would actually support panels, works out to less than about 80 contiguous square feet, the requirement can be waived on that basis too, independent of the size calculation.
Put those together and the honest picture is this: a studio-scale detached ADU has a real shot at skipping solar entirely on the size exemption alone. A one- or two-bedroom detached unit in the 800 to 1,200 square foot range that most Sacramento-region homeowners actually build is very likely past that threshold and needs a system sized to the calculation. Where exactly your specific floor plan lands isn't something to guess at from a square-footage rule of thumb; it's an actual calculation your architect or Title 24 energy consultant runs once the plan is set.
Curious where your planned unit size falls? SafewayQuickQuote.com factors in your project scope for a free estimate in about two minutes, or call (530) 204-8294 and we'll talk through the size math before you commit to a floor plan.
Battery Storage: What's Actually Required
This is the part homeowners tend to over-assume. A home battery is not required to satisfy the solar PV mandate on a detached ADU. The mandate is about the solar system itself, not storage.
Where it gets murkier is a separate, related provision some industry guidance describes as part of the 2025 Energy Code cycle: a requirement for battery-ready, or ESS-ready, wiring, meaning the electrical rough-in has to leave a clean path for a battery to be added later, even if no battery goes in now. There's also a documented mechanic where installing a qualifying battery alongside the PV system can reduce the calculated PV size that would otherwise be required, a tradeoff some homeowners use deliberately if roof space is tight.
We're being direct about the limits of what we could confirm here: we could not pull the exact code section governing the battery-ready wiring provision from a primary California Energy Commission source in time for this guide, so we're not printing it as settled fact with a citation attached. What we can tell you is that it's the kind of detail a licensed Title 24 energy consultant catches automatically during compliance documentation, the same person preparing your energy forms for the solar sizing calculation. It's not something you need to separately research or negotiate; it's baked into the standard design process on any project the mandate actually applies to.
What Solar Actually Costs on a Sacramento-Region ADU
Two different costs get lumped together here, and separating them matters for budgeting.
Title 24 energy compliance documentation. This is the paperwork and calculations proving the ADU's design meets the energy code, solar sizing included, prepared by an energy consultant as part of standard plan check submittals. Across our Sacramento-region ADU guides, including our published Elk Grove figures, this consistently runs $1,500 to $4,000. This cost applies whether or not solar ends up being required, since the energy documentation itself is a standard part of any new-construction ADU permit package.
The physical PV system. This is the actual hardware and installation, when the mandate genuinely applies to your unit. We don't have Sacramento-region-specific installed pricing to cite here, so we're using California-wide 2026 industry pricing instead, and saying so plainly: installed solar in California is running roughly $2.50 to $3.50 per watt in 2026. Applied to the size range most mid-size detached ADUs that clear the small-ADU exemption actually need, roughly 1.8 kW to 3.5 kW, that works out to a rough planning range of $4,500 to $12,000. Treat that as a starting point for budgeting, not a quote; your actual number depends on panel count, roof pitch, mounting complexity, and which installer you use.
One more cost note worth knowing, again sourced to broader industry reporting rather than a Sacramento-specific figure: the federal residential solar tax credit that used to offset roughly 30% of a purchased system's cost expired for residential systems at the end of 2025 under recent federal legislation. That's not tax advice, and your specific situation may differ, confirm current federal and state incentive status with a tax professional or your solar installer before budgeting around any credit.
| Item | Typical Range | Provenance |
|---|---|---|
| Title 24 energy compliance documentation | $1,500–$4,000 | Sacramento-region, consistent across our ADU guides |
| PV system, small-ADU exempt unit (under ~1.8 kW required) | $0 | Exemption applies; no system mandated |
| PV system, typical mid-size detached ADU (1.8–3.5 kW) | $4,500–$12,000 | California-wide 2026 industry pricing, not Sacramento-specific |
| Garage-conversion or attached ADU | $0 solar-related | Generally exempt as an alteration/addition, not new construction |
Base ADU construction costs in the Sacramento region still run $80,000-$160,000 all-in for a garage conversion, $145,000-$260,000 for an attached ADU, and $175,000-$340,000 for a standard new detached unit, consistent with what we've published across the rest of this cluster. Solar, where it applies, layers on top of the detached figure rather than replacing any of it.
Want a number that reflects your specific project? SafewayQuickQuote.com builds a free AI-powered estimate in about two minutes, or call (530) 204-8294 and we'll walk through whether your planned unit is likely to clear the exemption before you finalize a design.
Solar, Your Panel, and Your Utility: Three Separate Questions
Homeowners planning a detached ADU often assume solar, panel capacity, and the utility hookup are one conversation. They're related, but three different questions with three different answers.
Panel capacity is a load-calculation question: does your existing electrical service handle the ADU's own kitchen, HVAC, water heater, and laundry circuit stacked on top of what your house already draws. That's covered in our Sacramento ADU panel upgrade guide, and it's about consumption, not generation, a separate process from solar entirely.
Whether you need solar, and how big, is the Title 24 Part 6 question this guide covers.
Grid interconnection is your utility's own application, separate again, and it varies by address. SMUD serves the City of Sacramento, Elk Grove, and Folsom. PG&E serves Davis, Woodland, Dixon, and West Sacramento. Roseville runs its own municipal utility, independent of both. In unincorporated Yolo County, Valley Clean Energy generates the power, but PG&E still owns the lines and processes the connection. Net metering terms differ by utility; we're not printing specific rates here, since assuming one utility's program applies to another is exactly the kind of cross-market mistake that sets the wrong expectation. Confirm your specific program directly with whichever utility serves your address.
A detached ADU that needs both a bigger service and a PV system is running all three processes at once. Get your electrician and solar contractor talking to each other early in design, not after each has separately submitted paperwork, so the applications don't stall each other at inspection.
City-by-City: Reach Codes, and Why None Currently Stack On Top of the State Formula
Homeowners planning across this cluster reasonably ask whether Sacramento, Davis, Elk Grove, Folsom, Woodland, West Sacramento, Roseville, or Dixon layers its own, stricter solar rule on top of the state's Title 24 Part 6 formula. We looked for a city-specific solar amendment in each of these eight jurisdictions and found none. That's also unlikely to change in the near term, and there's a specific, verifiable reason why.
AB 130 (Chapter 22, Statutes of 2025), a state budget trailer bill effective June 30, 2025, froze state and local building standards affecting residential units from October 1, 2025, through June 1, 2031. Per the California Building Standards Commission's own guidance, cities and counties can't adopt new or modified local Title 24 amendments for residential units during that window, with only narrow exceptions: substantially the same as an ordinance already in effect as of September 30, 2025, an emergency health-and-safety finding, wildfire home-hardening, or an ordinance aligned to a general plan approved by June 10, 2025 that incentivizes all-electric construction. Outside those lanes, the door on new local energy amendments, including anything tightening solar requirements beyond the state's own formula, is effectively closed through mid-2031.
That freeze lines up with a real, current example. The City of Sacramento adopted an all-electric new-construction ordinance in 2021, limiting new natural-gas hookups in low-rise homes and smaller commercial buildings. According to local news reporting from around November 2025, the City Council voted to repeal it, following a federal appeals court ruling that undercut similar all-electric rules elsewhere and the broader shift AB 130 represents. Worth being precise about what that repeal touches: it's a gas-hookup policy, not the solar PV mandate. Title 24 Part 6's solar sizing rule is a separate, state-level requirement the repeal doesn't affect. We're flagging it because it's the clearest current example of local energy-policy amendments here getting pulled back, not expanded, the opposite direction a new local solar reach code would need to move.
Davis has, in past years, run its own voluntary all-electric reach code, an incentive-based program easing certain requirements for builders who choose all-electric over mixed-fuel. That's separate from the mandatory statewide solar sizing rule, and any change to it now runs into the same AB 130 freeze.
Elk Grove, Folsom, Woodland, West Sacramento, Roseville, and Dixon: we found no published local solar or energy reach code specific to any of these six beyond the state Title 24 Part 6 baseline. Confirm directly with the relevant building division before finalizing a design.
What We Verified, and What We Didn't
Verified: the Title 24 Part 6 versus CalGreen Part 11 distinction; the categorical exemption pattern for attached ADUs, conversions, JADUs, and factory-built units; the small-ADU exemption threshold of roughly 1.8 kW and its approximate correspondence to detached units under 600 to 700 square feet, corroborated across multiple independent industry sources; the limited-solar-access exemption around 80 contiguous square feet; AB 130's residential building-standards moratorium, verified directly against the California Building Standards Commission's own Information Bulletin 25-03, dated September 22, 2025; Sacramento's 2021 all-electric ordinance and its subsequent repeal, per local news reporting.
Not verified, deliberately not printed as settled fact: the exact California Energy Commission code section and subsection governing the ADU-specific PV sizing formula, referenced consistently across industry sources as Equation 150.1-C but not independently confirmed against primary CEC text for this guide; the precise code citation for the battery-ready wiring provision; any Sacramento-region-specific installed solar pricing, we used California-wide industry data instead and said so; and current net metering or interconnection rates for SMUD, PG&E, or Roseville Electric, which we're routing you to each utility directly rather than guessing at.
Confirm your specific project before finalizing a design: your city's Building Division for the energy plan check, and a licensed Title 24 energy consultant for the actual PV sizing calculation on your floor plan.
Frequently Asked Questions
Do all new ADUs in the Sacramento region need solar panels?
No. The mandate is a Title 24 Part 6 energy code requirement that applies to newly constructed, site-built detached ADUs. Attached ADUs, garage conversions, other interior conversions, JADUs, and factory-built ADUs installed on a permanent foundation are generally treated as alterations or fall under a separate regulatory track, not new construction, so the standard PV sizing requirement generally doesn't apply to them.
Is the ADU solar rule a CalGreen requirement?
No, and this is the most common mix-up. CalGreen is Title 24 Part 11, covering water efficiency, construction waste diversion, EV wiring, and material standards. Solar PV sizing is a Title 24 Part 6 requirement, the energy code, the same part that governs insulation, windows, and HVAC efficiency. Both parts get reviewed at the same plan check on a new ADU, which is why homeowners often assume they're the same rule.
What is the small-ADU solar exemption?
If the state's calculation, which factors in the ADU's conditioned floor area and climate zone, comes out under roughly 1.8 kW of required system size, no solar installation is mandated. In practice that threshold tends to land around detached ADUs under approximately 600 to 700 square feet, though the exact break point shifts with climate zone and roof orientation. A separate exemption applies if the usable, unshaded roof area is under about 80 contiguous square feet.
Does a new detached ADU need battery storage along with solar?
A battery itself is not required to satisfy the PV mandate on a detached ADU. Some 2025 Energy Code guidance describes a battery-ready, or ESS-ready, wiring provision meant to make a future battery easier to add, and installing a qualifying battery alongside the PV system can reduce the calculated PV size that's otherwise required. We could not independently confirm the exact code citation for the wiring provision, so treat it as something your Title 24 energy consultant will flag during design, not a separate mandate to research on your own.
What does solar cost on a Sacramento-region ADU in 2026?
Two separate costs are involved. Title 24 energy compliance documentation and design, the paperwork proving the ADU meets code, commonly runs $1,500 to $4,000 across our Sacramento-region ADU guides. The physical PV system itself, when the mandate actually applies, runs on California-wide industry pricing of roughly $2.50 to $3.50 per watt installed in 2026; a typical 1.8 kW to 3.5 kW system sized for a mid-size detached ADU lands in a rough planning range of $4,500 to $12,000. Treat both as planning ranges, not quotes, until an energy consultant and a licensed solar contractor run your specific numbers.
Do Sacramento, Davis, Elk Grove, Folsom, Woodland, West Sacramento, Roseville, or Dixon have their own local solar rules beyond the state mandate?
We found no city-specific solar amendment stacked on top of the state Title 24 Part 6 formula in any of these eight jurisdictions. That's also unlikely to change soon: AB 130 (Chapter 22, Statutes of 2025) froze state and local residential building standards, including local reach codes, from October 1, 2025 through June 1, 2031, with only narrow exceptions. Sacramento's own City Council repealed its 2021 all-electric new-construction ordinance around the same period, according to local news reporting, a separate gas-hookup policy, not the solar PV mandate itself, but a visible example of the broader pullback on local energy amendments happening right now.
Does adding solar to an ADU also require a panel upgrade?
Not automatically, and they're two different questions answered by two different professionals. A panel or service upgrade is about whether your electrical system can carry the ADU's new loads, kitchen, HVAC, water heater, laundry, covered in our Sacramento panel upgrade guide. Solar interconnection is a separate application with your utility, SMUD, PG&E, or Roseville Electric depending on your address, tied to the PV system itself. They sometimes happen on the same job, but loop your electrician and solar contractor in early so the two applications don't stall each other.
Can I avoid the solar requirement by building a garage-conversion ADU instead of a detached unit?
Generally, yes, because a garage conversion is treated as an alteration to an existing structure rather than new construction under Title 24 Part 6, so the standard solar mandate generally doesn't apply to it. That's a real cost advantage worth weighing alongside the other differences between a garage conversion and new detached construction, covered in our Sacramento garage conversion ADU guide, but it shouldn't be the only factor in the decision.
Related Guides
- Sacramento ADU Panel Upgrade Guide: SMUD Costs (2026)
- Sacramento Garage Conversion ADU Guide (2026)
- Elk Grove ADU Guide: Permits & Costs (2026)
- Roseville ADU Guide: Permits & Costs (2026)
- Sacramento ADU Guide: Permits, Costs & Rental Income (2026)
- Davis ADU Guide: Permits & Free Pre-Approved Plans (2026)
- Well & Septic Systems for Rural Sacramento & Yolo County ADUs (2026)
- Safeway ADU Cost Calculator
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