Over 1 billion people around the world lack access to electricity, and over 2 billion still cook with traditional biomass fuels, which cause significant mortality through respiratory disease. We study the factors affecting uptake of “modern” forms of energy like grid-supplied electricity, solar lanterns and solar home systems, and LPG (liquefied petroleum gas) as a substitute for biomass fuel. We also run randomized, controlled trials (RCT) to study the effect of these new energy sources on social welfare outcomes—like health, income, and educational attainment.