7.2 Prescriptive Requirements for Photovoltaic System

To comply with the prescriptive requirements, all low-rise single family and multifamily buildings are required to have a PV system installed unless the building qualifies for an exception. The minimum qualifying size of the PV system is based on the projected annual electrical usage as described by the Equation 7-1 below.

Table 7-1 – CFA and Dwelling Adjustment Factors

Climate Zone	A - CFA	B - Dwelling Units
1	0.793	1.27
2	0.621	1.22
3	0.628	1.12
4	0.586	1.21
5	0.585	1.06
6	0.594	1.23
7	0.572	1.15
8	0.586	1.37
9	0.613	1.36
10	0.627	1.41
11	0.836	1.44
12	0.613	1.40
13	0.894	1.51
14	0.741	1.26
15	1.56	1.47
16	0.59	1.22

7.2.2 Exceptions to PV requirements

Annual Solar Access: The annual solar access is the ratio of solar insolation including shading over the solar insolation without shading. Refer to Example 7-12 for an example of how to calculate solar access.

Effective Annual Solar Access: The effective annual solar access shall be 70 percent or greater of the output of an unshaded PV array on an annual basis.

Effective Annual Solar Access Roof Areas: Are roof areas that meet the Effective Annual Solar Access requirements and are at least 80 contiguous square feet.

There are six allowable exceptions to the prescriptive PV requirements as listed below.

Exception 1 may apply if there is limited unshaded roof space. No PV is required if the effective annual solar access is restricted to less than 80 contiguous square feet by shading from existing permanent natural or manmade barriers external to the dwelling, including but not limited to trees, hills, and adjacent structures.

Exception 2 may apply to climate zone 15 and the required PV size may be reduced, if there is inadequate space on the roof to accommodate the PV size specified in Section 7.2.1. The PV size shall be the smaller of a size that can be accommodated by the Effective Annual Solar Access Roof Areas, or a PV size required by the equation above, but no less than 1.5 Watt DC per square foot of conditioned floor area.

Exception 3 may apply to two stories residential buildings and the required PV size may be reduced if there is inadequate space on the roof to accommodate the PV size specified in Section 7.2.1. The PV size shall be the smaller of a size that can be accommodated by the Effective Annual Solar Access Roof Areas, or a PV size required by the Equation 150.1-C, but no less than 1.0 Watt DC per square foot of conditioned floor area

Exception 4 may apply to three stories or higher residential buildings and the required PV size may be reduced if there is inadequate space on the roof to accommodate the PV size specified in Section 7.2.1. In all climate zones, for low-rise residential dwellings with three habitable stories and single family dwellings with three or more habitable stories, the PV size shall be the smaller of a size that can be accommodated by the Effective Annual Solar Access Roof Areas, or a PV size required by the Equation 150.1-C, but no less than 0.8 Watt DC per square foot of conditioned floor area.

Exception 5 For a dwelling unit plan that is approved by the planning department prior to January 1, 2020 with available solar ready zone between 80 and 200 square feet, the PV size is limited to the lesser of the size that can be accommodated by the effective annual solar access or a size that is required by the Equation 150.1-C.

Exception 6 may apply to buildings with battery storage system. The required PV sizes from Equation 7-1 may be reduced by 25 percent if a battery storage system is installed. For single family building, the minimum capacity of the battery storage system must be at least 7.5 kWh. For multifamily buildings, the battery storage system must have a minimum total capacity equivalent to 7.5 kWh per dwelling. In all case the battery storage needs to meet the qualification requirements specified in Joint Appendix JA12 and be listed with CEC.

Example 7-1 Exceptions

Question:

I’m an energy analyst simulating a 2-story building, can you explain in plain English the requirements of exception 2 for climate zone 15, exception 3 for 2-story buildings, and exception 4 for 3-story buildings?

Answer:

Exceptions 2, 3, and 4 were created to account for unusual roofs that may not have enough space to accommodate the PV size that would offset the annual kWh of the dwelling. If the exception is used, the requirement is to install as much PV capacity as possible, but no less than 1.5 Wdc per square foot in CZ 15, or 1 Wdc per square foot for 2-story buildings, or 0.8 Wdc per square foot for 3-story buildings.

Example 7-2

Question:

How do you demonstrate compliance with the exception 3 to the PV sizing requirements for a 2-story building?

Answer:

If the energy analyst does not know have the roof layout plan or does not anticipate a roof area limitation issue, then the building must be modeled without the exception (prior to final approval, the energy analyst may update the simulation run and resubmit the updated CF1R, if the roof plans become available and indicate an area limitation issue). However, if the energy analyst has the roof plans that indicate area limitation, then exception 2 may be used to model the building. If the exception is used, then the energy analyst must specify, in the compliance software or CF1R, the maximum PV size that can be accommodated by the roof, but no less than 1 Wdc per square foot. If the exception is used, prior to final approval, proof must be provided that documents roof area limitations that justifies using the exception. Documentation may include roof plans, aerial photos, satellite images, 3D model, or other documentation that clearly shows the available roof areas that meets the solar access requirements.

Compliance with exceptions 2 and 4 follows the same procedure as above.

7.2.3 Joint Appendix 11 (JA11) Requirements

The installed PV system must meet the applicable requirements specified in JA11.

For prescriptive path compliance, if a PV system is installed with a pitch greater than 2:12 or 10 degrees, the arrays must be oriented between 90 to 300 degrees from true north. If the pitch is less than 10 degrees, then it is considered a low-slope (flat) installation, and orientation has insignificant impact on the array’s performance and therefore it can be ignored.

When using the performance approach, the array may be oriented in any direction, including due north; however, the more the orientation deviates from the optimum orientation of southwest, the worse the system performs, resulting in a larger PV system size needed to achieve compliance. So, it is best to orient the panels as close to southwest as possible to maximize the system performance with the smallest array size.

In order to use the California Flexible Installation (CFI) simplified modeling option in the performance method, the PV array must be installed between 150 to 270 degrees from true north, with all modules at the same tilt as the roof for pitches up to 7:12.

For prescriptive path compliance, the PV system must not have any obstruction to the array. Obstructions include the following:

(a) Any vent, chimney, architectural feature, mechanical equipment, or other obstruction that is on the roof or any other part of the building.

(d) Any tree that is planted on the building lot or neighboring lots or planned to be planted as part of landscaping for the building. (The expected shading shall be based on the mature height of the tree.)

(f) Any planned neighboring building or structure that is known to the applicant or building owner.

(g) Any telephone or other utility pole that is closer than 30 feet from the nearest point of the array.

In general, the distance between edges of the arrays and any obstruction must be at least twice the height of the obstruction that extends above the PV array as seen in Figure 7-1 below. Note that any obstruction located north of the array does not count as shading obstruction.

For performance path compliance, if there is any shading to the array, the detail orientation and location must be input in the software.

In summary, if the arrays are unshaded, then both prescriptive and performance methods can be used to demonstrate compliance with the Standards; however, if an array is shaded, then the detailed approach under the performance method must be used to model the actual shading conditions of the arrays. For more information on software inputs, please refer to the software user’s manual.

Example 7-3 Shading

Question:

What would be the impact of shading on the PV sizing requirement?

Answer:

Prescriptively the PV array cannot have any shading and must meet the minimum shading criteria in JA11. Under the performance path the shading condition must be modeled as it is present, and it will result in a larger PV size that meets the same TDV budget as a smaller unshaded PV system.

A solar assessment tool that is approved by the Executive Director must be used to document the shading conditions of the PV system. Measurements shall be made at all the major corners of the array. Additional measurements will be needed if they are more than 40 feet apart, and the additional points of measurement should be evenly distributed evenly. See Figure 7-2 for example of measurement locations for a typical roof.

Figure 7-2: Example of Points Where Measurement Shall Be Made Using a Solar Assessment Tool

The approved solar assessment tool can be a physical tool that measures the available solar energy at the installation site, or software based tool that model the physical features of the building and surrounding shading conditions including roofs and trees, and then calculates their solar potential by analyzing it against historical weather data.

The installer must provide documentation that verifies the shading conditions of the array(s). This is done by using a CEC approved solar assessment tool or CEC approved alternative verification method

Alternative Methods - Aerial photos that document the positions of shading obstructions in relation to the location of the array may be use as an alternative to solar assessment tools. These methods include satellite images, drone images, digital image taken using long masts or from adjacent high grounds or structures. These images must provide unobstructed, sharp, and clear view of the PV array(s) and nearby obstructions casting shadows. The images must document:

d. The horizontal distance between the obstruction(s) and nearest point of the array(s)

The Executive Director may approve additional alternate methods that can be used to evaluate the solar access availability of the location.

The PV system must have a web portal and a mobile device application that enable the occupants monitor the performance of their PV system, to identify, report, and correct performance issues with the panels, inverters, shading, or other issues that may adversely impact the performance of the PV system. At a minimum, the occupants must have access to the following information:

(c) Hourly (or 15-minute interval), daily, monthly, and annual kWh production in numeric and graphic formats for the system.

In addition to the requirements above, the PV system must also meet the following requirements in JA11:

Interconnection Requirements: All inverters in the PV system must comply with the CPUC Electric Tariff Rule 21, which governs CPUC-jurisdictional interconnections for all net energy metering (NEM) customers. Rule 21 requires that inverters have certain capabilities to ensure proper operation of the electrical grid as more renewables are interconnected. The inverters must perform functions that when activated, can autonomously contribute to grid support during excursions from normal operating voltage and frequency system conditions by providing dynamic reactive/real power support, voltage and frequency ride-through, ramp rate controls, communication systems with ability to accept external commands and other functions.

Certificates and Availability: The PV installer shall certify on the Certificate of Installation that all provisions of JA11 are met and provide PV array geometries used in the performance calculation if applicable. The Certificate of Installation shall be available on the building site for inspections.

Enforcement Agency Responsibilities: The local enforcement agency shall verify that the Certificate of Installation is valid complete and correct, and uploaded into a Commission-approved registry.

Example 7-4 Remote Monitoring

Question:

How do I implement monitoring to meet section JA11.5.1 including the current reading?

Answer:

There are multiple options. Many inverters can connect via ethernet and wireless to the homeowner’s internet, and others use independent cellular connections. For cellular, the data should be updated to the monitoring portal periodically as allowed by the cellular plan.