ADU with solar panels on the roof in California

Solar Requirements for ADUs in California

Solar Requirements for ADUs in California

California, often considered the golden state for renewable energy, has been at the forefront of the solar revolution in the United States. Recognizing the importance of clean energy and its role in combating climate change, the state has implemented various regulations and incentives to promote the adoption of solar energy. One such initiative addresses the solar requirements for Accessory Dwelling Units (ADUs). ADUs, also known as granny flats or in-law units, are secondary housing units on a single-family residential lot. They can be attached to the primary residence or be stand-alone structures.

The Rise of ADUs

The housing crisis in California has led to an increased interest in ADUs. These units are seen as a solution to provide affordable housing, reduce urban sprawl, and increase property values. In response to this trend, the state of California has enacted legislation to make it easier for homeowners to build ADUs, eliminating certain zoning restrictions and reducing permit fees.

Solar Mandate for New Homes

In 2020, California became the first state to require all new homes to have solar panels. This groundbreaking mandate, known as the California Solar Mandate, applies to new single-family homes and multifamily buildings up to three stories, including condos and apartments. The California Energy Commission (CEC) believes that this initiative will lead to significant energy savings and reduce greenhouse gas emissions.

Do ADUs Fall Under the Solar Mandate?

The question many homeowners have is whether ADUs fall under this solar mandate. If a new ADU is detached from the primary residence, it must comply with the solar requirements. This means that the combined solar system for both the primary residence and the ADU should meet the energy needs of the entire property. If the main residence already has solar panels, it is possible to exempt the ADU if it meets the Title 24 specifications for energy sufficiency.

However, if an ADU is attached onto the main house, it is then considered an addition, and is therefore exempt from the solar mandate. This is also true if an existing part of the house is converted into an ADU, including garage conversions, whether they are attached or detached.

It is possible to get an exemption, or variance, from a city if the ADU is in the shade for a significant amount of time. In this case, solar panels are generally not recommended as they lack efficiency. Cities have requirements for Helioscope reports or other forms of measurements that solar experts can perform to determine the amount of shading on a property.

Benefits of Solar on ADUs

  1. Energy Savings: Solar panels can significantly reduce electricity bills. With the rising cost of electricity, having a solar system can lead to substantial savings in the long run.
  2. Increased Property Value: Studies have shown that homes equipped with solar panels have higher property values compared to those without.
  3. Environmental Impact: Solar energy reduces reliance on fossil fuels, leading to a decrease in greenhouse gas emissions. This is particularly important in California, which aims to be carbon-neutral by 2045.
  4. Incentives: Homeowners can benefit from federal tax credits, state incentives, and local rebates when installing solar panels.


As California continues its push towards a sustainable and green future, understanding the solar requirements for ADUs is crucial for homeowners. While not all ADUs are mandated to have solar panels, the benefits of installing them are undeniable. From cost savings to environmental impact, solar energy is a wise investment for any property owner.

To schedule a free consultation and rough estimate, please reach out to Superior ADUs. Enter your information in the web form, give us a call, or send us an email anytime.

Phone: 949-216-0686


Solar Panel Installation on ADUs in california.

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