As of Jan. 1st, 2020, all new homes built in California will be required to have solar photovoltaic systems. The ruling is part of the California Energy Commission's newly-instituted 2019 Building Energy Efficiency Standards, aimed at reducing greenhouse gas emissions "by an amount equivalent to taking 115,000 fossil fuel cars off the road."

Along with the addition of solar panels, new California homes will also have to meet updated thermal envelope standards, which prevent heat transfer from the building's interior to the exterior and vice-versa. Ventilation systems that minimize air pollution from both outdoor and indoor sources will additionally be required.

And yes, these requirements will initially cost homeowners more money, although they should save cash in the long run.

According to the California Energy Commission, adhering to the 2019 standards will add about US$9,500 to the cost of constructing an average new home, but then decrease energy and maintenance costs by $19,000 over the next 30 years. Stated otherwise, the commission estimates that based on a 30-year mortgage, homeowners will pay about $40 more per month for an average home, but save $80 a month in heating, cooling and lighting bills.

All told, homes built in accordance with the 2019 standards should use about 53 percent less energy than those built under the existing 2016 standards. Over the following three years, this should reduce the state's greenhouse gas emissions by 700,000 tonnes (771,618 tons).

"Under these new standards, buildings will perform better than ever, at the same time they contribute to a reliable grid," says Commissioner Andrew McAllister, the Energy Commission's lead on energy efficiency. "The buildings that Californians buy and live in will operate very efficiently while generating their own clean energy. They will cost less to operate, have healthy indoor air and provide a platform for 'smart' technologies that will propel the state even further down the road to a low-emissions future."