In an era of U.S. energy abundance, the persistently high energy bills paid by low-income households is troubling. After decades of weatherization and bill-payment programs, low-income households still spend a higher percent of their income on their electricity and gas bills than any other income group. Their energy burden is not declining, and it remains persistently high in particular geographies such as the South, rural America, and minority communities. As public agencies and utilities attempt to transition to a sustainable energy future, many of the programs that promote energy efficiency, rooftop solar, electric vehicles, and home energy storage are largely inaccessible to low-income households. This review describes the ecosystem of stakeholders and programs, and identifies promising opportunities to address low-income energy affordability, such as behavioral economics, data analytics, and leveraging health care benefits. Scalable approaches require linking programs and policies to tackle the complex web of causes and impacts that financially constrained households face.