Appetite, mostly. Utilities want stable production so have been slow to embrace renewables at high penetration (even though the economics are there). The excep

Appetite, mostly. Utilities want stable production so have been slow to embrace renewables at high penetration (even though the economics are there). The exception the U.S. is Texas with over 50% wind at night, because the utilities don't have much say in the production portfolio (it's heavily deregulated). For distributed rooftop solar, consumers are much more swayed by the savings, so many solar companies find it easier to sell hundreds of systems directly to consumers instead of one system to utilities. This is changing slowly, because the economics are getting too much for utilities to ignore, but unfortunately federal rules like the clean power plan will likely be made toothless soon, so many utilities will continue to be stuck in the mud.