Editor’s note: This story has been updated.

Vail Resorts and New Belgium Brewing are among the companies urging the Colorado Public Utilities Commission to hold co-op utilities to rigorous renewable energy goals.

“Require wholesale co-ops to conduct a more thorough analysis of the cost of existing resources and alternatives to fossil fuels, including storage and renewable energy,” the letter from the Ceres BICEP Network reads. “The analysis should also align with state public policy objectives, including Colorado’s goal to reduce greenhouse gas emissions 90% by 2050.”

The network is a coalition of 55 businesses that advocates for clean energy policy.

In an e-mail, the organization singled out Tri-State Energy for not moving quickly enough toward renewable sources.

“The BICEP Network urges the PUC to require Tri-State and other wholesale co-ops to use their [energy resource plans] to conduct a more thorough cost analysis of existing resources and fossil fuel alternatives, including renewable energy, energy efficiency and energy storage,” a spokesperson wrote. “These alternatives are often more cost-effective than the investments Tri-State has chosen to date.”

Mark Stutz, a spokesperson for Tri-State, noted that in the company’s four-state operating region, “approximately 31% of the electricity used by our 43 member cooperatives and public power districts comes from renewable resources. Two new projects have been announced this year that will take us to approximately 45% by 2023.”

The legislature this year required wholesale electric cooperatives to submit an electric resource plan for approval by the PUC. Proposed rules from the PUC require the plans to contain “the cost of the projected carbon dioxide emissions” using the federal government’s social cost of carbon.

Under Colorado’s renewable energy standard, co-ops with fewer than 100,000 customers must generate 10% of their electricity from qualifying renewable sources by 2020. Tri-State, which powers 18 of Colorado’s 22 co-ops, is at 13%.