Enel doesn't do grid edge halfway. The Italian utility-turned-global-renewable-energy-developer rolled out smart meters to 100 percent of its Italian home and business customers in 2001 -- and achieved payback on the investment within four years.

Nearly every utility is turning to renewable energy, but Enel's green power division has installed 36 gigawatts of capacity across 24 countries. It will eventually take over the company's entire generation business, due to a corporate goal of 100 percent renewable energy by 2050.