This introduction presents an overview of key concepts discussed in the subsequent chapters of this book. The book talks about a key aspect of such uncertainties by examining the challenges of developing sustainable heating systems in European cities. Cities are both major producers of greenhouse gases (GHG) emissions, and highly vulnerable to the impacts of resulting climate change. The liberalisation framework is formally indifferent to climate change, and its suitability to meet radically changed requirements, including the need for long-term planning for a low energy, low carbon system, is contested. The aims of energy policy have changed from an emphasis on economic modelling to maximise formal cost efficiency to a more complex set of goals. The book evaluates the comparative prospects for sustainable heating for European cities, and the likelihood of greater deployment of district heating in the UK, under current policy and market arrangements.