My electric co-op in WI, despite pressure has refused to purchase solar or wind power. If I recall correctly, their charter requires them to act in the interests of members, thus no expensive power. Passing the cost along as a corporation responsible to shareholder would, is a non starter. My guess this isn't a position all co-ops take.
I live in a pretty remote rural area-our co-op gets over 50% of it’s power from wind and solar-they also own an interest in those wind and solar farms, so the cost is the same or less than before-they also encourage individuals to install solar panels for their own use with a sizeable rebate. Since we are far out here, they also provide the least expensive broadband and land line service-I have the whole thing and my bills are lower than my non-co-op acquaintances in the city, 50 miles away...