The dependence on oil and other fossil fuels for over 80% of our energy and the continued emission of carbon dioxide threatening stable climate are captured in a single term: sustainability. Although we generally agree that sustainability is valuable, there is less agreement on how much sustainability is necessary or desirable. In this talk, three criteria describing increasingly strict features of sustainability will be presented and applied to evaluate the alternatives to oil and carbon dioxide emission, such as tapping unused energy flows in sunlight and wind, producing electricity without carbon emissions from clean coal and high efficiency nuclear power plants, and replacing oil with biofuel or electricity. The implementation of these more sustainable alternatives will require new cost effective nanoscale materials. The successful development of such materials will have a marked impact on the production of energy in a sustainable and environmentally benign fashion.