Almost half of the biggest U.S. companies have established clean-energy targets for themselves, according to a report Tuesday from sustainable investors and environmental groups including the World Wildlife Fund.

It’s not just the biggest U.S. companies -- 44 percent of the smallest 100 members of the Fortune 500 have also set goals, up from 25 percent in 2014, and 48 percent of the entire list.

Many are finding that renewable energy isn’t just cleaner, it’s also often cheaper. About 190 Fortune 500 companies collectively reported about $3.7 billion in annual savings, according to Power Forward 3.0, a report by WWF, Ceres, Calvert Research & Management and CDP.