During the transition to the solar age an energy gap will have to be filled. In this context coal may emerge as a source of hope, particularly when oil and later also natural gas have become scarce and thus expensive.The prerequisite, though, is that efforts to engineer coal's transformation into a clean energy source with a neutral impact on the climate are successful. The transition period in which coal is indispensable could be limited, however. But this would require swift progress on renewable energies as well as on hydrogen research. Breakthroughs by backstop technologies such as nuclear fusion need much more time. Until then, coal will be of the essence.