BOSTON (AP) — Gov. Deval Patrick has signed an energy bill that requires Massachusetts utilities to buy more of their electricity in competitively bid, long-term contracts with renewable energy providers.

Patrick said Friday the new law will protect ratepayers while also helping the environment by requiring more use of clean energy sources.

Starting in 2016, utilities would be required to purchase 7 percent of their power from long-term renewable contracts, up from 3 percent.

The measure also includes several other provisions, including a higher cap on net metering, which allows people who use solar panels or other renewable energy sources to sell more of their power back to electricity distributors.

Attorney General Martha Coakley says the law updates the state’s Green Communities Act and will bring greater competition, accountability and transparency.