Since the start of the 21st century, the U.S. energy system has changed tremendously. Technological advances in energy production have driven changes in energy consumption, and the United States has moved from being a net importer of most forms of energy to a declining importer—and a net exporter in 2019. The United States remains the second largest producer and consumer of energy in the world, behind China. The electric power industry faces uncertainty over how to address transmission and reliability within an environment of aging infrastructure, potential cybersecurity threats, and continued interest in renewable energy and other low carbon sources of electricity. Reliability and electricity prices are complicated by environmental regulations, the rising availability of natural gas for electricity generation, and the intermittent nature of renewables. Renewable energy consumption nearly doubled between 2000 and 2019, primarily due to increased use of wind and solar for electric power generation and biofuels for transportation. New electric power capacity additions for wind and solar have exceeded those for coal and natural gas in four of the last five years. Small-scale solar, which is of particular interest because it rarely requires new transmission infrastructure, can be installed in a variety of geographies, and may financially benefit individuals and communities. Renewables also include hydropower, geothermal energy, and other types of biomass. Each energy product (e.g., heat, electricity, and liquid fuels) derived from these sources has a unique market and policy considerations. Adoption of energy-efficiency technologies in buildings, transportation, and industry may support policy objectives toward energy security and reducing energy consumption (e.g., consumers saving money, avoiding greenhouse gas emissions). Policy options include mandatory efficiency standards and programs encouraging adoption of existing technologies, among others. Resulting changes in energy consumption may also be impacted by changes in demand for energy services.