It was aimed at what might be needed if the price of solar-powered electricity came down. NRECA began working with a small group of local and wholesale co-ops. It published training manuals like “The Communicator’s Toolkit,” which suggested ways to minimize the risk of using solar while capturing its benefits. That was timely because in 2015 the price of solar energy began to crash. “We happened to be in the right place at the right time to pull together our co-ops,” Spiers explained in an interview.Previously, the niche for solar in rural areas was mainly individuals putting rooftop solar on their homes. The new goal that emerged among co-ops was to connect as many local members as possible to nearby arrays.Some members lived in apartments without solar. Co-ops developed “virtual net metering,” which meant customers could still buy access to a solar project and get credit on their utility bill without connecting to the array.Meanwhile, Tri-State has built the largest wholesale solar supply system serving co-ops in the United States, even as it has tried to limit the amount of solar that co-ops can generate. Another wholesaler, Great River Energy of Maple Grove, Minn., built 19 solar arrays that served co-ops across the breadth of the state.Then Great River had to figure out how to adjust its system to cope with cloud patterns that slowly drifted across the state, cutting electricity at one co-op and increasing it at another.The Poudre Valley Rural Electric Association in northern Colorado built two solar arrays that were quickly sold out. Then it developed a cheaper third array by bringing in an outside group called Grid Alternatives that used volunteers and donated materials. That helped Poudre attract more low- and moderate-income families and nonprofits.Finding cleaner, closer power sources has helped trim NRECA’s traditional reliance on coal from 54 percent in 2014 to 40 percent in 2017.