The energy transformation process beginning to take place in many countries as a response to climate change will reduce substantially the consumption of fossil fuels, but at the same time cause a large increase in the demand for other raw materials. Whereas it is difficult to estimate the quantities of, for example, iron, copper and aluminium required, the situation is somewhat simpler for the rare elements that might be needed in a sustainable energy economy based largely on photovoltaic sources, wind and possibly nuclear fusion. We consider briefly each of these technologies and discuss the supply risks associated with the rare elements required, if they were to be used in the quantities that might be required for a global energy transformation process. In passing, we point out the need in resource studies to define the terms “rare”, “scarce” and “critical” and to use them in a consistent way.