California is now the first US state to mandate solar panels on new homes and apartment buildings built after January 1st, 2020.
It's the next big step towards ending greenhouse gas emissions.
According to the state law, it already requires that 50% of all electricity comes from non carbon- emitting sources by the year 2030.
It has been noted that the solar panel mandate will add around $8,000 to $12,000 to a home's cost.
According to the Energy Commission, they estimated that homeowners will only see an additional $40 to monthly mortgage payments.
The commission said they will save $80 on heating, cooling and lighting costs per month.
Builders will have the option of adding solar panels to individual homes or building shared power systems for a group of homes.
California has now invested of $42m in solar energy to date and the mandate will give it an ever bigger boost to the solar industry.