The California Energy Commission voted Wednesday in a 5 to 0 vote to adopt the policy as part of the state’s Building Energy Efficiency Standards. The California Building Standards Commission will need to give the final approval before the mandate can be enacted. It is expected to support the energy commission’s vote.

The mandate, which will change the building code for residential buildings up to three stories high, aims to increase the amount of solar energy used in the state. Three years ago, California Gov. Jerry Brown signed legislation that requires at least 50% of the state’s electricity to come from renewable energy by 2030.

There is a cost. The solar panel mandate is expected to add an average of $9,500 to the cost of a new home. However, proponents argue that it will also help raise the value of the home and attract buyers who will benefit from lower electricity bills.

“This is an undeniably historic decision for the state and the U.S. California has long been our nation’s biggest solar champion, and its mass adoption of solar has generated huge economic and environmental benefits, including bringing tens of billions of dollars of investment into the state,” Solar Energy Industries Association CEO Abigail Ross Hopper said in a statement. “Now, California is taking bold leadership again, recognizing that solar should be as commonplace as the front door that welcomes you home.”

Hoff acknowledged that other states may not be ready to follow California’s lead. Still, Hodd said she remained hopeful that some will adopt similar policies once leaders in those states see the benefit of California’s mandate.