ADUs are incredibly popular in California, and as such, the state has always sought to improve laws around the requirements when constructing any type of accessory dwelling unit. One particular aspect of this has been the California ADU solar requirements, in line with the recently updated Title 24. If you plan to build any type of ADU, you will be required to meet certain standards per local and state law. A solar panel system falls under those standards, and here is everything you need to know about whether or not your ADU will require them.

Are Solar Panels Required For ADUs In California?

In California, newly built Accessory Dwelling Units (ADUs) that are detached and not manufactured are required to comply with the Energy Code, which includes the provision of solar panels. This requirement is to ensure that the energy consumption of the ADU is offset by solar energy.

However, it’s important to note that the solar panels do not have to be physically installed on the ADU itself; they just need to contribute to its energy offset. Starting from January 1st, 2023, there is an exemption in place: If the Photovoltaic (PV) capacity listed on your Title 24 is less than 1.8 kWdc, then solar installation is not required.

The law Title 24, is a building standards code first enacted in 1978. The changes regarding ADUs and the requirement to provide solar panels took effect on Jan 1st, 2020. The new changes state that installing solar panels to ADUs will be required if the accessory dwelling unit falls under one of the following three categories:

  • Newly constructed (after Jan 1st, 2020)
  • Non-Manufactured
  • Detached

Although this seems cut and dry, there are some differing requirements for ADUs and exemptions, depending on which zone you live in; we’ll go into those shortly. Always check with your local housing authority to be 100% sure.

ADU SOLAR REQUIREMENTS

Title 24 ADU Solar Energy Requirements

Regarding solar energy, the requirements of Title 24 are that all detached ADUs, newly constructed after January 1st, 2020, must have a PV system to provide solar energy. There are several exemptions to Title 24 around solar systems for those about to build ADUs.

Beyond the exemptions, other types of ADUs don’t require solar installation; these include:

If you have any doubts about what Title 24 means for your ADU construction, speak with your builder or local authority for clarity.

ADU Solar Exemptions

SOLAR PANEL

Now, let’s understand what kind of ADUs are not required to install a PV system (solar panel or photovoltaic system). Beyond the exemptions we’ve just discussed, attached ADU, etc., there are also exemptions based on the size of the detached ADU and the climate zone in which you live.

This latter point is important here, as you must know in what climate zone you are living in. Here, we will use Los Angeles as an example. If you live in L.A., you will most likely be in Zones 10, 9, 8, or 6. The zone that you live in will dictate how big your detached ADU can be before your solar panel installation is required.

  • Zone 6 – 942.76 net square feet
  • Zone 8 – 716.72 net square feet
  • Zone 9 – 701.46 net square feet
  • Zone 10 – 606.06 net square feet

These variations in the law are based on the energy efficiency standards in each geographical location, which is why they vary in such a small area. As you can see, you must know which zone you are building your ADU.

Additional exemptions may apply to you that won’t require you to install a PV system. Here are the specific details referring to some of the more nuanced exemptions.

  • Conversion accessory dwelling units are considered by the law as ‘additions’, including both attached and detached, and will not require the installation of a PV system
  • The government states that if there is not enough surface area with unshaded solar access, also known as restricted effective annual solar access, installing solar will not be required
  • Homeowners can meet their requirement to provide solar panels for an ADU by adding a PV system to the primary house, thus exempting the ADU from requiring a solar system.

    Given this range of detailed and, in some cases, specific exemptions, you may need to seek out professional advice from those in the know. If you live in L.A., for example, you’ll need to know in what zone you live, how much surface area is unshaded, and whether or not your project is considered an ‘addition’ or a new construction.

    This is precisely why you need a reputable ADU builder who can advise you on your solar panel requirements for your new construction.

    How Much Does It Cost To Add Solar Panels to an ADU?

    Now, if you are required to add solar panels to your accessory dwelling unit, your next thought will probably be, how much will that cost? The bad news is that a solar system for an ADU comes in at between $12,000 to $18,000. This includes the cost of the solar panels and the installation.

    The good news is that you can save money on your energy bills going forward, as you’ll be using solar energy rather than taking it from the grid. In some cases, we see homeowners get involved in ‘net metering,’ where they can actually sell solar energy back to the grid.

    Those upfront costs may not be what you want to hear, given the amount you’ll already be spending on your accessory dwelling unit. But in the long term, it does make for a sound investment.

    California Solar Incentives and Tax Credits 2023

    After the new Title 24 was enacted, the state also introduced a range of tax credit incentives and rebates to soften the blow of the cost for those who need to install solar panels. Here, we will showcase just some of the incentives, with the average dollar amount you could receive in California, for having to install solar panels on your ADU.

    Self-Generation Incentive Program (SGIP)

    Rebates for installation of batteries alongside your solar panels – Up to $200 per kWh of battery installed.

    Single Family Affordable Solar Homes (SASH)

    Affordable financing for individuals who qualify (means tested) – As much as $3 per watt, potentially around $18,000 per year.

    Equity Resiliency Program

    Rebates for installing batteries with your solar panels – $1,000 per kWh battery, installed in qualifying areas.

    Federal Solar Tax Credit

    This fantastic tax credit system aims to reduce your costs for installing solar panels, increase the volume of renewable energy in the state, and reduce its carbon footprint. These are your income tax liability credits based on when the solar panels are installed.

    • 30% for systems installed between 2022 and 2032
    • 26% for systems installed in 2033
    • 22% for systems installed in 2034
    • The program will be discontinued in 2035 and will no longer be available

    As you can see here, numerous incentives and tax credit opportunities are aimed at increasing the number of residents using solar energy.

    How Many Solar Panels Will I Need for My ADU?

    ADU SOLARAssuming that your ADU requires a PV system, you must calculate precisely how many solar panels you will need. The exact calculation that the government uses is based on climate zone, size of ADU, and electrical usage.

    Let’s start with the scientific bit; the exact calculation used for the number of solar panels on newly constructed ADUs is the following:

    kW (PV)required = (CFA x A)/1000 + (NDwell x B)

    This is each aspect of the formula explained:

    • kW(PV) = kW(DC) size of the PV system
    • CFA = Conditioned floor area
    • NDwell = Number of dwelling units
    • A = Adjustment factor
    • B = Dwelling adjustment factor

    Now, this may sound very confusing, but there is a variation in both adjustment factors based on where you live. This calculates just how many panels you need to meet the solar energy requirements.

    Just to reiterate, this is not something that you should worry too much about, but it is the conversation you’ll have with your ADU builder before they install solar panels.

    In simple terms, a general rule here in California is that most accessory dwelling units will require at least eight solar panels, and if the ADU is larger than 1,000 square feet, it will need more. Homeowners must meet these exact solar energy requirements to obtain any available solar tax credit incentives.

    Working With The Best ADU Builders

    Given the specifics of the requirements included in Title 24 concerning ADU construction, it is always a smart idea to contact a high-quality and reputable builder with experience. They will be able to explain and advise on these rules of both constructing accessory dwelling units and the California energy code.

    Always seek references, especially those who have had ADUs built since January 1st, 2020, and ask any questions about what solar power looks like on your property. If you’re ready to get started, contact us at Build Method Construction, and we can deliver the perfect ADU for you that meets all state requirements around solar energy.

    We have delivered excellence for our customers across California for over 25 years, and we can use that same professionalism and expertise on your next ADU project. Call today for a free quote.

    FAQs

    Are There Additional Incentives For Adding Solar Energy?

    Yes. There are tax credits and rebate incentives once you install solar panels to your ADU.

    Will Adding Solar Panels Be Required If I Am Converting An Existing ADU?

    Adding solar panels will not be required if you are converting an ADU built before January 1st, 2020.

    Can I Expect Energy Savings If I Comply With Solar Requirements?

    You can expect energy savings and a more energy-efficient ADU when installing solar panels. This is true even if the ADU is an existing detached building conversion.

    What Happens If I Don’t Meet Solar Requirements For My ADU?

    Failure to comply with the solar requirements per Title 24 will result in a warning and a fine if you still fail to comply.