Example of building a 2,000 sq. ft. two-story residential building:
kWpc = (2,000 sq. ft. conditioned floor area x climate zone 7 CFA adjustment factor of 0.572) = 1144/1000 = 1.144 + (1 dwelling x dwelling zone 7 adjustment factor B of 1.15) = 1.15
A 2.294 kWpc (DC) PV system is required = 1.144 + 1.15.
You work the math backward to get your minimum required solar PV size.
Using a 350-watt premium PV panel, that would be 7 PV panels (measuring approximately 40 x 67 inches each).
Exceptions to PV Requirements formula:
1. less than 80 sq. ft. of unshaded roof space from permanent barriers (trees, hills, structures). No PV is required.
2. climate zone 15 only may reduce PV size if not enough roof space for full system per formula but no less than 1.5 Watt DC per sq. ft. of conditioned floor area.
3. applies only to two-story residential buildings and allows for a reduction of PV system size if roof space is limited but no less than 1.0 Watt DC per sq. ft. of conditioned floor area.
4. applies to three stories or higher residential buildings and allows for a reduction of PV system size if roof space is limited but no less than .08 Watt DC per sq. ft. of conditioned floor area.
5. if the dwelling was permitted before January 1, 2020, with 80 – 200 sq. ft. of solar-ready roof space, then you may install the lesser of the result of their new formula, or what fits in the available roof space with effective solar access.
6. the required PV system size may be reduced by 25 percent if a battery storage system is installed. For a single-family dwelling, the minimum capacity of the battery storage system must be at least 7.5 kWh.
For multi-family dwellings, it must be 7.5 kWh per dwelling.
Battery backup systems also must meet qualifications specified in Joint Appendix JA12 and be certified and listed with CEC.
In addition, the PV system must be permitted, interconnected to the local utility company and meet their equipment requirements, and provide remote energy production monitoring.
Shading and roof orientation play a role.
A solar assessment tool must measure and record annual projected shading from each roof orientation.