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. 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 the Power Forward 3.0 report. Potential savings and sustainability goals prompted corporations to buy almost 3.7 gigawatts of power generated by clean-energy projects in 2015, and another 2.5 gigawatts last year, almost all from wind and solar, according to Bloomberg New Energy Finance. Technology companies including Google and Apple are among the biggest buyers of clean energy.