Climate change, pollution, and energy insecurity are among the greatest problems of our time. Addressing them requires major changes in our energy infrastructure. Here, we analyze the feasibility of providing worldwide energy for all purposes (electric power, transportation, heating/cooling, etc.) from wind, water, and sunlight (WWS). In Part I, we discuss WWS energy system characteristics, current and future energy demand, availability of WWS resources, numbers of WWS devices, and area and material requirements. In Part II, we address variability, economics, and policy of WWS energy. We estimate that similar to 3,800,000 5 MW wind turbines, similar to 49,000 300 MW concentrated solar plants, similar to 40,000 300 MW solar PV power plants, similar to 1.7 billion 3 kW rooftop PV systems, similar to 5350 100 MW geothermal power plants, similar to 270 new 1300 MW hydroelectric power plants, similar to 720,000 0.75 MW wave devices, and similar to 490,000 1 MW tidal turbines can power a 2030 WWS world that uses electricity and electrolytic hydrogen for all purposes. Such a WWS infrastructure reduces world power demand by 30% and requires only similar to 0.41% and similar to 0.59% more of the world's land for footprint and spacing, respectively. We suggest producing all new energy with WWS by 2030 and replacing the pre-existing energy by 2050. Barriers to the plan are primarily social and political, not technological or economic. The energy cost in a WWS world should be similar to that today. (C) 2010 Elsevier Ltd. All rights reserved.