California’s solar access laws appear in the state’s Civil, Government, Health and Safety, and Public Resources Codes. California’s Civil Code (801.5) ensures that neighbors may voluntarily sign solar easements to ensure that proper sunlight is available to those who operate solar energy systems. California’s Government Code (65850.5) provides that subdivisions may include solar easements applicable to all plots within the subdivision in their plans. California’s Public Resources Code (25980) contains the Solar Shade Control Act, which encourages the use of trees and other natural shading except in cases where the shading may interfere with the use of active and passive solar systems on adjacent properties. Specifically, the law provides that a tree or shrub cannot cast a shadow which covers more than 10 percent of a solar collector's absorption area at any one time between the hours of 10 a.m. and 2 p.m. if the tree or shrub is planted after the installation of the solar collector.
[http://www.leginfo.ca.gov/pub/07-08/bill/sen/sb_1351-1400/sb_1399_bill_2... SB 1399] of 2008 amended the Public Resources Code to exempt trees and shrubs planted prior to the installation of a solar system. Also exempted are trees and shrubs that are subject to a local ordinance, or the replacement of trees or shrubs that had been growing prior to the installation of the solar device.