Maine lawmakers have passed a bill that moves up the state’s timeline to reach net zero carbon emissions.

The new law would require the state’s energy office to expand Maine’s existing Renewable Portfolio to 90% by 2040, focusing on rooftop wind, solar, and battery storage produced here in the state. The remaining 10% will be dedicated to a new category of clean resources, like hydropower.

Achieving 100% clean electricity could lower average household energy costs by about $1,300 per year, according to a study conducted by the state’s energy office last year. That’s because pricing can be volatile for fuels sourced out-of-state, like natural gas and heating oil.

A previous law signed by Mills in 2019 had set a goal of 100% clean energy by 2050.