The California Energy Commission (CEC) has defined 16 distinct climate zones, which help determine the minimum solar PV system size required for new construction.
Our brand-new California Solar Mandate Calculator can help you determine the climate zone based on your ZIP code.
Simply enter your ZIP code into the box and click anywhere on the page to pull the climate zone information.
If you are having trouble with a ZIP code, you can also use the CEC’s website app to quickly determine the climate zone from an address. Click here to access the tool.
Once the tool loads, type your address into the search bar and press enter. The result shows the building climate zone:
You can then enter this result back into our California Solar Mandate Calculator.
How does the climate zone affect the calculation of the minimum PV system size?
According to the CEC, the DC system size is calculated from the following formula:
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 = CFA adjustment factor
B = Dwelling adjustment factor
Factors A and B are defined by the climate zone as follows:
A word of caution... The formula above is a "base" or "initial starting point" for system size. There are exceptions and modifiers that can affect the minimum PV size, including annual solar access and exemptions for community solar. Also, there’s a Joint Appendix (JA11) with more specific details (qualifications) required for the PV system to be compliant, including solar access, azimuth range, and obstruction proximity.
Stay tuned for more articles explaining these conditional requirements!