"Just one percent of the rural population in Sierra Leone has access to energy. No television in the evening, no outlets for charging phones, no lights to turn off before going to sleep—just darkness. Meanwhile, those with energy access are “energy poor,” spending an unsustainable percentage of their household income on an irregular supply of energy. In many countries in sub-Saharan Africa, like Sierra Leone, energy expenditure can exceed 9 percent. In contrast, households in wealthier countries normally spend only 1-2 percent.
One method for reducing the energy burden of low-income households is the pay-as-you-go (PAYG) model, which allows customers to pay installments of as much as they can afford to access electric light. In the PAYG model, customers take home an off-grid solar home system and repay over time. (Here, “off-grid” refers to households that are equipped with their own personal solar panel that is connected to a desk lamp, set of hanging bulbs, or other solar light product). Companies remotely control functionality of the lights. When customers repay their weekly balance, either through an agent or through mobile money, they receive a code via SMS that allows them to ‘unlock’ their product for a week’s worth of energy."
Read more here: http://blogs.ei.columbia.edu/2017/09/25/alumni-startup-brings-pay-as-you-go-solar-energy-to-sierra-leone/