Of all the measures of the continent's poverty, few are starker than that about two-thirds of its people have no access to reliable electricity. But thanks to a happy combination of innovation and falling costs for renewable energy, Africa may now be able to leapfrog ahead not once but twice, skipping both polluting fossil fuels and, often, the electricity grid itself. This is partly due to falling costs: the price of solar panels has come down by more than 80% since 2010, and that of wind turbines is also dropping fast. Yet generating power is useful only if it can be sent to where it is needed, and in many parts of Africa electricity grids seldom stretch beyond big cities. [A] set of innovations is offering to sidestep this problem with mini rooftop solar installations that can power a home, or slightly larger micro-grids" that can light up a village. Rooftop solar systems usually consist of a small solar panel and a small rechargeable battery and controller which typically powers ... lights, a radio and a phone charger. Most systems have a built-in connection to the mobile-phone network that allows the provider to switch it on or off remotely. Instead of shelling out $250 or so upfront for an entire system, customers can buy electricity for the equivalent of 50 cents a day using mobile money. Thanks to this new "paygo" model, venture capital is pouring into an industry that now has at least half a dozen significant firms. The largest of them, M-Kopa, has electrified more than 500,000 homes and is adding almost 200,000 more a year.