Off-grid energy, long the focus of nonprofits and governments, is becoming the next massive investment opportunity for the world’s biggest energy players, with hundreds of millions of dollars going into solar home systems and other energy solutions for the billions of people who lack access to reliable grid power, or any power at all. That’s the conclusion of a new report from Wood Mackenzie Power & Renewables and Energy4Impact, detailing the spectacular rise in investment in the off-grid energy access sector.