HyreADU
Design your ADU Explore ADU Options

ADU builders

ADU solar installation: is it required?

By the HyreADU research desk. Last checked .

The short answer

ADU solar installation is required in California only when the ADU is a newly constructed building under the Energy Code, which in practice means a new detached unit.

Conversions and new attached units are additions and are outside the rule. Even for a new detached unit, no solar is required if the formula gives a system under 1.8 kWdc.

Test one: new building or addition

The California Energy Commission classifies a detached, newly built ADU as a new building. Converted space, a JADU, and a new unit attached to the house are additions. Additions are outside the prescriptive solar requirement in Energy Code section 150.1(c)14.

Test two: the size formula

For new buildings, the required system size comes from a formula using floor area and climate-zone factors. Exception 2 says no system is required when the result is less than 1.8 kWdc. Our ADU solar research runs the formula for an 800 square foot unit in all 16 climate zones; seven fall below the line.

Hiring a solar installer

Solar work in California needs a contractor with the right license, often a C-46 Solar or C-10 Electrical. Check it on the CSLB site. Ask whether the system ties to the ADU’s own meter or the main house, and how that affects your utility account. Your Title 24 consultant confirms the size first.

What to do next: read the questions to ask an ADU builder, check what decides ADU cost, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.

Get ADU options

Questions

Does a garage conversion need solar?

No. Under the CEC’s classification it is an addition.

Can the ADU share the main house’s solar?

Possibly, if the system and service allow it. Ask your installer and utility.

Does my city have extra solar rules?

Some cities adopt local reach codes. See all-electric reach codes.

Is ADU solar a tax question?

Tax credits are a tax matter. HyreADU gives no tax advice.

Sources

HyreADU is a publisher. It does not design, permit or build ADUs, has no partner builders, and gives no legal, tax or engineering advice. Rules vary by state and city; California rules are labeled as such.