Current debates about a more sustainable energy system strongly emphasise the role of CO2 emissions and climate change. Without denying the urgency of reducing CO2 emissions, it is important to recognise that this is only one of several categories of requirements for creating a more sustainable energy system. This chapter discusses three of these categories: (1) access and security, (2) climate change and environmental impact,(3) economic and social development. The problem of dealing with three different perspectives is illustrated with reference to the development of concentrated solar power. It is clear that a more sustainable energy system cannot be achieved using the simple creed that renewables reduce CO2 emissions and are therefore good. Understanding the different issues that need addressing may not in itself resolve disagreement, but will at least create a common understanding of what is involved.