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Written by Hannah Seeger from itty bit Better
California gained its nickname "the Golden State" from the gold rush back in the 1800s. Today's glow isn't coming from the gold, poppies, or even the Golden Gate bridge. It is coming from the sun shining on all the solar panels. California is leading the country in solar power generation.
The rise in solar has been a result from government incentives and 292 out of 365 days of the year having sunshine in Downtown Los Angeles. It begs the question, is Florida really the sunshine state?
Since January 1, 2020 the building codes require solar panels on new construction single-family homes and low-rise multi-family homes up to three stories.
With 80% of the year having sunshine, we are beginning to see why solar became a mandate. In this article let's stick with some of the details you may be looking for.
Title 24 is California's Building Energy Code. It is "designed to reduce wasteful and unnecessary energy consumption in newly constructed and existing buildings", says energy.ca.gov. It is nothing new. Title 24 has been around since 1974, making it the first energy regulation commission, called the California Energy Commission. Today, California continues to lead the country in energy efficiency advancements, including solar.
The code is updated every 3 years and since January 1, 2020 it has contained a solar mandate for new residential construction. The code includes "solar ready" requirements for all new construction containing conditioned spaces.
In this article we are focusing on low-rise residential, which is either a single family home or a multi-family home under three stories.
In short, if you are building a new single family home or a multi-family home under three stories you are required to have a solar system. The code further outlines where to place the system, how big it needs to be, orientation, monitoring requirements, and exceptions.
Before we get into the nitty gritty of some of the requirements, we recommend getting assistance from an architect, contractor, energy engineer, or city building planning official. The building codes can get confusing quickly, even for experienced individuals. So seek advice from people who have specific experience with the mandate.
- Whether this is new construction, an addition, alteration, or repair
- Which compliance method you will follow (Prescriptive or Performance)
- Prescriptive Method allows your building to comply by following a type of checklist
- Performance Method allows your building to comply by calculating an estimated performance of your buildings energy usage by using one of the approved software platforms (completed by an engineer)
- There are different exceptions to both Prescriptive and Performance Methods
If you are following the Prescriptive Method, use this formula to calculate the solar system size:
**_kWPV = (CFA x A)/1000 +(NDwell x B)_**
kWPV = kWdc size of the PV system
CFA = Conditioned floor area
NDwell = Number of dwelling units
A = Adjustment factor from Table 150.1-C
B = Dwelling adjustment factor from Table 150.1-C
If you are following the Performance Method the steps aren't as straightforward. The building location, construction materials, estimated occupants, appliances, lighting, and the solar system specifications are needed to calculate the expected energy consumption of the building.
The total building energy consumption is scored based on the Energy Design Rating (EDR). The EDR determines whether the building complies with the code.
Everyone’s house is different. What if you don't get enough sun? What if the roof isn't big enough? Does a battery storage affect the system requirements?
California's Solar Mandate says "This is part of California's plan to reduce the carbon footprint in residential new construction". Luckily, the code offers flexibility in how that is accomplished.
Exception 1: If the available space is less than 80 square feet and is shaded by things without your control (trees, hills, structures)
Exception 2: Climate zone 15 (Palm Desert area) is allowed the smaller system size of either the available space or the calculated equation size, but no smaller than 1.5 Watt DC per square foot of conditioned floor area.
Exception 3: If the house has two habitable stories, it is allowed the smaller system size of either the available space or the calculated equation size but no less than 1.0 Watt DC per square foot of conditioned floor area.
Exception 4: If the house has three habitable stories, it is allowed the smaller system size of either the available space or the calculated equation size but no less than 0.8 Watt DC per square foot of conditioned floor area.
Exception 5: If you happen to have plans approved before January 1, 2020, and you have 80-200 of space that is solar-ready, you can choose the smaller size of either the available space or the calculated size from the equation.
Exception 6: The solar system size may be reduced by 25% if it is installed along with a battery energy storage system.
Exception: If the newly constructed house is built in a community where there is a shared solar system that serves residents the same benefits compared to owning their own.
If you are looking for more details, energy.ca.gov has some great resources for understanding what you need to do for your specific situation. Look for the PDF provided by Ace, the PDF document contains easy-to-understand definitions and instructions on how to follow the code. Within the PDF, they link to sections of the code if you need to reference it.