Most of the world's energy comes from fossil fuels. Carbon-based fuels are stores of high quality solar energy accumulated over millions of years, for example, by photosynthesis capturing carbon and storing it in woody biomass, then through a serious of processes eventually storing it as coal. The production of the fossil fuel supply base has been a very slow process. Use of this resource has been profligate with many predicting that we have now reached the point of peak production for oil and shortly that of gas. This point, termed Peak Oil, is where consumption exceeds production and it was first conceptualized by Marion King Hubbert. The combustion of fossil fuels releases carbon dioxide into the atmosphere and this enhances the natural greenhouse effect. It is accepted that the release of carbon is accelerating climate change. The concerns around a diminishing resource base and the impacts of climate change are shaping energy policy and technological development. This chapter will examine the current supply position for oil, gas and coal and predictions of use. It will then look at a number of supply-side technological developments.