The deployment of renewable energy systems, such as solar energy, to achieve universal access to electricity, heat and transportation, and to mitigate climate change is arguably the most exigent challenge facing humans today1,2,3,4. However, the goal of rapidly developing solar energy systems is complicated by land and environmental constraints, increasing uncertainty about the future of the global energy landscape5,6,7. Here, we test the hypothesis that land, energy and environmental compatibility can be achieved with small- and utility-scale solar energy within existing developed areas in the state of California (USA), a global solar energy hotspot. We found that the quantity of accessible energy potentially produced from photovoltaic (PV) and concentrating solar power (CSP) within the built environment (‘compatible’) exceeds current statewide demand. We identify additional sites beyond the built environment (‘potentially compatible’) that further augment this potential. Areas for small- and utility-scale solar energy development within the built environment comprise 11,000–15,000 and 6,000 TWh yr−1 of PV and CSP generation-based potential, respectively, and could meet the state of California’s energy consumptive demand three to five times over. Solar energy within the built environment may be an overlooked opportunity for meeting sustainable energy needs in places with land and environmental constraints.