Digest of the Upcoming Mandatory Residential Solar Requirement

California is a well-known champion of emissions reduction, renewable energy, and green technology. In 1947, it became the first state to regulate air pollution, a bold measure for its time. In 2008 the state outranked its previous ambitions with targeting zero-net-energy use in all new homes and commercial buildings by 2020 and 2030, respectively.

With all new homes set to produce as much energy as they use by next year, it’s not surprising that each new edition of the energy code has raised renewable energy standards. In 2016, it introduced the so-called solar-ready requirements, which were aimed at preventing obstructions to future installation of solar systems.

The newest edition, effective from January 1st, 2020, requires all low-rise residential buildings to be fitted with a photovoltaic (PV) energy generation system.

If you are planning to build a home once the new code comes into effect, you should take the time to understand the following factors: system sizing, pitch and orientation, minimal shading requirements, as well as the energy savings and cost implications of installing a PV system.

PV System Size

In the context of a PV system, the term “size“ refers to the system’s output. The home’s Conditioned Floor Area (CFA) and Climate Zone determine the size, which can be calculated using the  formula and table below :

System Size (kW) = (Conditioned Floor Area x Value in Column A)/1000 + (Number of Dwellings x Value in Column B)

PV System Size Calcuation Adjustment Factors
Climate Zone A B
1 0.793 1.27
2 0.621 1.22
3 0.628 1.12
4 0.586 1.21
5 0.594 1.06
6 0.572 1.23
7 0.586 1.15
8 0.613 1.37
9 0.627 1.36
10 0.836 1.41
11 0.613 1.44
12 0.894 1.4
13 0.741 1.51
14 1.56 1.26
15 0.894 1.47

Per the calculation, a new single family home with 2,000 ft⊃2; of enclosed, conditioned space will require a PV system with an output of 2.23 kW in San Diego, 2.42 kW in Los Angeles, and 2.38 kW in the Bay Area.

Once you know the capacity of the system you will need, you can conceptualize its location on your roof. At this point, you will probably wonder how the system’s capacity translates into dimensions and costs.

A typical solar panel is made up of rows of 6 x 6 inch cells, and on average generates 290 watts. In residential applications, the best-fitting and most popular panel size is 65in x 39in, while most commercial buildings can house longer, 77in x 39in panels. This means that the 2.48 kW system on the home in Los Angeles will need at least 9 panels and cover an area of roughly 18 ft2.

With system costs averaging $4.06/watt in California as of August 2019, homeowners in this example would spend roughly $10,069 on their system before the federal tax credit, and $7,048 after.

The new energy code provides some exceptions to the solar system requirements.

A region’s climate impacts the effectiveness of a solar generation system. If you are building a home in Climate Zone 15, which covers the notably hot and sunny South-Eastern corner of the state, your PV system must generate at least 1.5 watts per square foot of the home’s CFA. In a home with 2,000 ft⊃2; of enclosed, conditioned space, this exception allows a 3 kW PV system whereas the formula above would call for 4.59 kW.

The new energy code lessens the PV system size requirements for buildings with multiple stories. Residential buildings with 2 habitable stories require systems with a minimum output of 1.0 watt/ft2; of CFA, while those with 3 habitable stories must generate at least 0.8 watt/ft2; of CFA.

Installing a battery along with the PV system is another way to reduce the system’s size by 25%. To be eligible for the reduction, the battery must have a capacity of 7.5 kW or more.

Access to sunlight is critical to a PV system’s function, and some homes may not have it due to barriers, such as trees, hills, and taller buildings. If a permanent barrier limits solar access to your roof to 80 contiguous square feet or less, your building does not require a PV system.

Pitch and Orientation

To be effective, a PV system’s pitch and orientation must be optimized to maximize solar exposure. The pitch is the slope at which the panel is installed, and the orientation is the direction in which the panels face relative to true North.

The 2019 Building Energy Efficiency Standards’ prescriptive compliance method requires all PV systems with a pitch greater than 10° to be installed within the azimuth range of 90° to 300°, measured from true north, clockwise. Systems that do not fall within this range must have their orientation described in the performance method. If a system is being qualified through the California Flexible Installation performance calculation, then the modules must fall between the azimuth range of 150° to 270°, and have the same tilt as the roof for pitches up to 30°.


Minimal Shading 
Roofs have plenty of projecting items that may cast a shadow on a PV system. To ensure that the building’s design precludes shadows from affecting solar generation, the 2019 energy code requires the distance between obstructions to sunlight and PV panels to be at least twice their height above the roof plane. This requirement applies to the following items given they are not located north of the PV array. 
  • Architectural features and equipment installed on the roof 
  • Neighboring buildings, terrain, and trees
  • Planned structures known to the applicant or building owner
  • Any utility pole located 30 feet or less from the nearest point of the solar array 

In some cases, fulfilling the minimal shading requirement may be a challenge. Mature trees and existing structures may be too close to the new building’s roof before its plan is even drawn. In such instances, your best bet is to qualify the PV system through the performance approach. 

Other Requirements

Plenty of other requirements exist in the 2019 Building Energy Efficiency Standards, and you can find them all here. It‘s important to remember that non-state authorities having jurisdictions may add their own details and nuances as they adopt the standards, so it’s best to consult your local building official before purchasing the system. 

Energy Savings and Cost Implications 

Whether California will reach its 2020 zero-net-energy goal for new residential buildings remains to be seen. That said,  according to estimates  from the California Energy Commission (CEC), homes built with 2019 standards will use 53% less energy than those built with the 2016 code. A laudable achievement? No doubt. But what do the new Title 24 requirements mean for the average homeowner’s bottom line?

CEC estimates that the 2019 standards will add $9,500 to the cost of building a new home, but save $19,000 in energy and maintenance over 30 years. Based on a mortgage amortized over the same duration, the new standards will add ~$40 to each monthly mortgage payment, but save ~$80 monthly on energy costs.

While the cost of installing a PV system may seem high at an estimated average of $8,400, there are options for reducing the cost. If you plan to pay for the system in 2020, you can still take advantage of the federal solar tax credit, better known as the Investment Tax Credit (ITC).

Most solar state rebates are exhausted, but you can still get a 100% property tax exemption on value added by the panels if you install your system before the end of 2024.

A few local incentive programs exist as well, but if none are available in your jurisdiction, you can still find affordable financing options through the Property Assessed Clean Energy Financing (PACE) program.

Design Everest Can Help 

Your solar system needs to be supported without damage to your roof, and must withstand wind and earthquake loads. Our engineers can furnish thorough plans and calculations for these supports. We understand that this is an extra cost for you, and will do our best to find the most cost-effective solution that keeps your solar system safely secured. What’s more, we will make sure that your solar permit gets approved without hassle. Call us at (877) 892-0292 for a FREE consultation and quote. We can also connect you with a professional engineer or designer right away for a virtual consultation or virtual on-site!

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