Solar for Your ADU: Meeting Title 24 Requirements

Ever since lawmakers took down the roadblocks to the construction of Accessory Dwelling Units (ADUs) in 2017, California has witnessed a spike in the construction of these affordable homes. As of 2022, nearly 24,000 ADU permits were issued by the state.


However, the California Building Standards Code (CBSC) has made revisions to Title 24, leading to some confusion for homeowners with ADUs.


What’s the change, and how can you ensure your ADU meets the latest Title 24 requirements? This guide outlines all you need to know.

What Is Title 24?

title 24 requirements

Title 24 is a set of legal mandates that outlines Building Energy Efficiency Standards for existing and newly built residential properties. The rules of Title 24 are designed to regulate energy usage to reach the state’s goal of net zero emissions by 2045.


Title 24 is reviewed and revised every three years, while the California Energy Commission (CEC) is responsible for the execution of these mandates.


These updates ensure that homeowners’ upgrades are cost-efficient and energy-efficient and will remain so for 30 years or longer. The mandates vary depending on climate zones and building type to account for regional differences.

Revisions to Title 24

Part 6 of Title 24, which came into effect in 2020, made it mandatory for newly built homes to have solar setups. This includes single-family homes, condos, and apartments built for residential use.


The latest revisions to Title 24 came into effect in January 2023. According to the new updates, all newly constructed ADUs are expected to have solar panels.


That said, the Title 24 mandate is subject to certain terms and conditions:


    1. All ADUs built for single-family homes must have solar provisions. The solar setup must produce enough energy to offset the in-law suite’s annual electricity consumption.
    2. It is not required to install the solar setup on top of the ADU. However, it should be placed somewhere on the ground, in the main house, or other practical locations.
    3. The rule applies to all newly constructed, non-manufactured, and detached ADUs. So, if you applied for an ADU permit after 1 January 2020 or built the unit after 31 December 2019, you must follow these updated regulations.
    4. ADUs must also adhere to other guidelines related to energy efficiency standards for lighting, heating, ventilation, and air conditioning systems.


As per these regulations, solar installations for ADUs built before 2020 aren’t required. However, investing in solar energy is a wise choice, irrespective of the Title 24 requirements, because it can grant you energy independence.


Given multiple rate increases, unpredictable natural calamities, and the dwindling reserve of fossil fuels, going solar is undoubtedly a wise choice for homeowners. But more on that later. Let’s see if there are any exceptions to the Title 24 mandates. Turns out, there are.

Exceptions and Exemptions from Title 24 Solar Requirements

California’s general solar mandate does not apply to houses with small roofs. If your property lacks the space for a rooftop solar installation and experiences excessive shading that makes solar an impractical choice, then you’re an exception.


You also will not be required to have a personal solar setup if you have access to community solar.


So, if your home qualifies under any of the conditions discussed above, would your ADU need a mandatory solar arrangement? There’s no definite answer to that question, and a few grey areas can be confusing if you want to build an ADU right now.

New Additions

For example, any additions to your existing home or alterations to the structure may not qualify as new construction. In such cases, you may not be required to adhere to the Title 24 solar mandates. Similarly, garage conversions and attached ADUs may not require an independent solar setup.


Tiny homes that can be considered as manufactured units may also be exempt from the rules.


However, a word of advice to the wise: do not take these matters lightly. It is important to consult your local solar provider and local authorities to determine whether the rules apply to your property.


Going solar has long-term advantages in 2024 and beyond. You should certainly consider solar panels for your home to futureproof it and embrace an eco-conscious lifestyle.

What Are the Cost Implications of Solar for Your ADU?


By conservative estimates, single-family homes with ADUs may require a 2.7 to 5.7 kW solar setup to offset their power consumption. As a homeowner, you should consider the cost implications of getting solar for your ADU—and it’s a huge concern for many.


Installing solar to your ADU could increase the upfront development cost of single-family homes by $8,400. Depending on your current use case and household size, add an estimate of $12,000 to $18,000 in costs for adding solar to your ADU.


Note that all homeowners are eligible for solar rebates and the federal tax credit because Title 24 concerns detached ADUs. You can also secure solar credit on a pro-rata basis for the ADU’s consumption if the primary home and the in-law unit are attached.


Depending on your income level, you can make some savings on your solar investment for your ADU. More importantly, solar pays for itself in the long run. While the upfront costs may seem quite high or even prohibitive, you can rest assured that you will be able to get a good return on your investment when you continue using solar.


To sum up, Title 24 might have mandated that newly built ADUs have solar power, but even without these regulations, investing in solar energy is a wise choice.

Invest in Solar Power to Futureproof Your Home

Whether you plan on building an ADU in the future, already have a permit for it, or own your home in California, you should seriously consider investing in solar.


Why? Because with a robust solar installation, you can:

Gain Energy Independence

You do not need to worry about energy usage during planned or unplanned power outages for your local grid. Even during emergencies like wildfires or floods, your home can function normally.


If you decide to couple your solar arrangement with a battery backup system, you can continue enjoying the perks of solar power even at night or in bad weather conditions.


Title 24 provides guidelines for battery purchase and usage. Alternatively, you can seek help from a solar advisor and professional installer.

Save on Your Utility Bills

In addition to reducing your carbon footprint and embracing an eco-conscious lifestyle, going solar can save you big on your utility bills. Going solar saves you 50% to 70% on your annual expenses. Whether you’re a grid-tied user or have your own energy storage system, this safety net will empower you.


Your local utility provider may continue pressing for rate increases, but having a solar energy plus storage system can help you control your expenses.

Increase the Value of Your Real Estate Investment

Going solar has the potential to increase the valuation of your home. So, if you plan on selling your property or renting it out in the future, an eco-friendly and solar-powered home (or ADU) will fetch you an excellent price in the market.


Solar power is one of the best home improvement investments you can make and continue enjoying for decades.

Authored by Ryan Douglas

Authored by Ryan Douglas

NRG Clean Power's resident writer and solar enthusiast, Ryan Douglas covers all things related to the clean energy industry.