加州打算直接從法律上規定從 2020 年開始的新房子都要有太陽能：「California set to become first US state requiring solar panels on new homes」。
The state’s Energy Commission is due to vote next week on new energy standards that would require virtually all new homes to be constructed with solar panels from 2020.
如果通過的話，從 20% 直接變成強制性的 100%：
Currently around 20 per cent of single-family homes are constructed with solar capacity built in, but if the new standards are approved as expected this proportion will rise sharply.
舊金山通過在 2017 年之後的建築物必須有 15% 的屋頂面積必須是太陽能相關的設備：「San Francisco Is Requiring Solar Panels on All New Buildings」：
The ordinance, passed unanimously by the city’s Board of Supervisors, extends an existing California law which requires 15 percent of roof space on new buildings to be “solar ready” — available and unshaded. That ordinance applies to residential or commercial buildings 10 stories or shorter.
Under the new ordinance, which will go into effect in 2017, new buildings need to have solar energy of some kind installed, either electricity-generating panels or solar heating units.
希望在 2020 年達到 100% 再生能源的目標：
San Francisco took a major step toward its own goal of meeting the city’s electricity demands with 100 percent renewable energy by 2020.
This week, San Francisco became the first major U.S. city to require all new buildings to have solar panels on their roofs, according to Scott Wiener, the city supervisor who introduced the bill.