Energy systems are undergoing a significant shift to renewable energy (RE). To date, the surface area required for RE systems is greater than that for non-RE systems, exacerbating existing environmental policy challenges, from increasing land competition, to visual impacts. A suitable metric for comparing the extent of systems is the power density of electricity production, that is, the electrical power produced per horizontal m(2) of surface area. This study systematically reviews power densities for 9 energy-types (wind, solar etc.) and multiple sub-types (e.g., for solar power: PV, solar thermal) in the United States. Median, mean, and uncertainty estimates are provided for 177 different densities from the literature. Non-renewable power densities are found to be three orders of magnitude larger than renewable densities. Natural gas and solar energy yield the highest median density per non-RE, and RE system respectively. Solar energy was the only system to experience a significant, positive relationship in power density over time. We apply these density estimates to NREL scenarios of future energy systems for state-specific assessments, and find that the largest growth in land use is in the southern United States.