Squaw Valley USA placed first and Alpine Meadows ranked third in the annual evaluation of 82 western ski resorts.
Paul Joyce is with the Colorado-based Ski Area Citizens Coalition which put out the list. He says they grade resorts on several areas.
"For example, buying renewable energy, producing renewable energy on site, recycling, buying snowmobiles that are four-cycle rather than the old two-cycle, updating their snowmaking equipment to make it more efficient - things like that."
Sugar Bowl and Boreal received A grades while Bs when to Kirkwood, Homewood, Sierra-at-Tahoe and Mount Rose.
Officials with the California Ski Industry Association say the grades reflect a growing priority among Sierra resorts to increase energy efficiency.