Co-op solar boom raises questions about coal in utility power mixes

"Tri-State has a significant amount of solar and procures almost a third of its power from renewables," Mark Dyson, an Electricity Practice Principal with think tank Rocky Mountain Institute (RMI) and lead author of the new report, told Utility Dive.

RMI found the costs of utility-scale solar and wind are so low that acquiring them can save Tri-State customers as much as $600 million through 2030 "even if it continues paying for and running the coal plants," Dyson said.

Tri-State does not doubt the importance of adding more solar and other renewables to its power mix. It does, however, question the accuracy and value of RMI's conclusions. But if the think tank is right, the remarkable boom in solar for co-ops, their power providers and other load serving entities may be just getting started.