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An overview of the California solar mandate

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If one state leads the rest of the country in setting the bar for solar, it’s California: the Golden State consistently tops the Solar Energy Industries Association’s list for the best states for solar, having more than four times the installed capacity than the runner up (North Carolina). 

While California has an abundance of sunshine, that’s surprisingly not the primary reason for the prevalence of solar panel installations throughout the state. In fact, much of California’s success in solar is the result of forward-thinking policies set by the state government, from the California Solar Initiative (CSI) to its ambitious clean energy goals.

The future of solar in the Golden State is looking brighter than ever thanks to the new, first-of-its-kind California solar mandate, a recent code that requires new homes to be built with a solar electricity system. In this article, we’ll give an overview of the mandate, as well as go over some costs and savings estimates for future homebuyers in California. 

What is the California solar mandate?

The California solar mandate is a new building code that requires new construction homes to have a solar photovoltaic (PV) system as an electricity source. This code, which goes into effect on January 1, 2020, applies to both single-family homes and multi-family homes that are up to three stories high. 

The solar panel system needs to be large enough to meet the annual electricity usage of the building; given that electricity usage can be difficult to determine in new construction projects, builders use an estimate for each property that’s based on the building’s floor space and the climate zone in which it’s located.

However, there is flexibility when it comes to sizing the solar panel system: for one, builders can decrease the size requirement of a system on a property by incorporating battery storage into the building. In fact, you can reduce the required size of the solar panel system by as much as 25 percent when you pair it with a solar battery, such as the Tesla Powerwall or LG Chem RESU10H. Plus, by incorporating energy efficiency measures or other demand-responsive measures into building design alongside battery storage, the required PV system sizes can be downsized by 40 percent or more.

Exceptions to the California solar mandate

There are a few types of new residential construction that are exempt from the code. In some cases, properties with a small enough roof or those that receive an abundance of shade may be exempt from installing a PV system. Additionally, building developers are welcome to pursue and build community solar projects, as opposed to rooftop solar panel systems for each property, so long as they receive approval from both the California Clean Energy Commission (CEC) and the local utility company. Any community solar project offered in lieu of on-site solar needs to offer similar benefits to the new homeowner that a rooftop or ground-mounted system located on their property would provide.

California solar mandate costs and savings numbers

The California Clean Energy Commission conducted a cost-effectiveness study to determine cost and savings implications for Californians purchasing a single-family home under these new building codes. They found that, with the solar panel requirement, the cost of a newly constructed single-family home will increase by approximately $8,400, equivalent to roughly $40 extra per month in mortgage payments. (Note: they calculated this estimate using a cost assumption of $3.10 per watt for the installed solar panel system, slightly higher than the average cost of solar quoted for California properties on the EnergySage Solar Marketplace.)

However, the CEC also predicts that while upfront costs of new homes will increase, the savings benefits for new homeowners far outweigh these initial costs. Assuming an average electricity rate of approximately 18 cents per kilowatt-hour (kWh), the state estimates that single-family homeowners will save about $80 a month on electricity costs. These monthly electricity bill savings, combined with paying an extra $40 each month in mortgage payments for the solar panel system, means new homeowners will come out with $40 net savings each month. Annually, this comes out to $500 per year in savings. Should electricity prices continue to rise and the cost of solar continue to fall, these savings numbers only stand to increase.

California solar mandate by the numbers

  • Additional upfront cost to new single-family homes: $8,400
  • Cost equivalent in mortgage payments: $40 per month
  • Electricity bill savings: $80 per month
  • Net savings: $40 per month, $500 per year

You can learn more about these numbers and assumptions used in calculations on the CEC’s frequently-asked-questions page.

Compare your own solar options today

Whether you’re building a home in California or another state, it’s worth exploring your solar options. If you’re interested in seeing what you can save with a solar panel system, our free-to-use Solar Calculator gives you ballpark estimates for both costs and savings with installing solar on your home or business. When you’re ready to take the next step, register for the EnergySage Solar Marketplace to receive and compare up to seven custom solar quotes online from local installers.

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About Kerry Thoubboron

Kerry has worked in solar for 5 years, starting out as an Energy Advisor helping customers compare their options and, ultimately, make well-informed solar decisions. She graduated from Boston University with a degree in Environmental Analysis and Policy. Outside of work, you can find Kerry snowboarding, watching The Office, or having passionate debates about which New England state is best (spoiler: it's Vermont).

5 thoughts on “An overview of the California solar mandate

  1. Mike Robertson

    I just read the portion of the California Civil Code dealing with the implementation of the solar mandate.

    I may be wrong but it does NOT appear to require all new homes to be equipped with PV packages.
    All single family homes created by a recent subdivision of TEN homes or more are obligated to do so.

    No reference is made to the people that buy a parcel of land and build a single home. There is a significant number of homes constructed this way in the unincorporated areas of California. Are they intended to be included in this mandate ?? Anyone care to weigh in ??

  2. Robert Range

    What about when the solar panel system breaks down or needs repairs and or replacing. My mom’s system needs a new main board and although it is under warranty the company hasn’t been so fast to replace it, 3 month and still no solar but I tell you what is still working…. the interest rate and the loan she needed to purchase the darn thing

  3. Berndt Nording

    The benefit calculations are WAY off. So the cost of a new home increases by $8400. You save $0 per month on your electricity bill. In the long run you still save $0, and after 25-30 years you are out the $8400. Why? Because this mandate requires YOU to pay for the solar installation but does NOT mandate your utility to allow connecting that system to the grid. And yes, there are utilities in California that figure they can make a lot more money by charging 32 cents/kwh and refusing to allow rooftop solar. After all, they have a monopoly…

  4. Vidya Vijayaraghavan

    The benefit calculations are a little off. We are trying to buy a 2900 sqft home. The builders mandate the purchase of solar from them for an additional cost of 23000$ when we can easily get it for less than 10,000 elsewhere. Where is the consumer benefit here???


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