California became the first state in the country Wednesday to require that new homes have solar panels on their roofs.

The mandate, which takes effect in 2020, won unanimous approval of the California Energy Commission. One commissioner predicted the “green” lifestyle regulation will eventually go national.

“We are the first, we will not be the last,” said commissioner David Hochschild. “This is a landmark vote today.”

Commissioner Andrew McAllister said the roof-top solar mandate isn’t a “radical departure,” but instead “one piece of an overall policy sweep that California has to reduce greenhouse gas emissions” and make new homes more energy efficient.

McAllister said he believed the solar industry is now mature enough and ready for the mandate.

The solar rules will apply to new single-family homes and new multi-family housing of three stories or fewer. Under the plan, builders who obtain construction permits issued on Jan. 1, 2020 or later must comply.

Some new houses will be exempt if solar panels are infeasible, such as when a roof is in the shadows of another structure.

The state exempted taller housing structures where there is not enough rooftop space to handle residents’ electric needs. In some instances, the solar requirement can be met through a shared installation within a community.

The new regulations will not apply to remodels.

The requirements are likely to add nearly $9,500 to the construction cost per home as state officials have declared a housing crisis. Home prices have soared in California, and housing stock has failed to keep up with demand.

Energy Commission spokeswoman Amber Beck said the agency estimates that the typical monthly mortgage payment could rise by $40 as a result of a higher home prices, but increased energy efficiency will cut monthly utility bills by about $80.

The commission also adopted new standards that are expected to increase the energy efficiency of attics, walls, insulation and windows.

Testifying Wednesday at the commission hearing, a representative from a coalition of major gas and electricity providers, including the Sacramento Municipal Utility District, said utility companies approved of the changes, calling them cost effective and technically feasible.

The California Building Industry Association, which represents new homebuilders, has expressed reservations about the new rules, saying it wished the state would have postponed the regulations for two years.

But the group’s technical director Robert Raymer said the BIA is supportive of the effort. He called the proposed changes “a quantum leap in statewide building standards.”

“We especially appreciate the CEC’s willingness to work with industry to reduce overall compliance costs and provide design flexibility,” Raymer said in a press statement. “Among other things, the CEC is providing significant compliance credit for the installation of battery storage technology.”