Something unusual is happening in Hawaii: An electric utility and rooftop solar installers have agreed upon a proposal to reward households for sharing clean energy with the grid at useful times. In many places around the US, utilities treat rooftop solar as an obstacle; utilities in California are currently urging regulators to levy a monthly fee on anyone who adds rooftop solar. But things are playing out differently on Oahu. Hawaii’s most populous island, with a million residents, is struggling to ramp up enough clean energy ahead of shutting down its largest fossil-fueled power plant in September. To that end, the monopoly utility, Hawaiian Electric, teamed up with advocates of customer-owned energy to say households should earn money for using solar and batteries to keep power flowing to the grid.