Open Access

The concept of sufficiency - reducing energy uses beyond technical efficiency - is far-reaching and requires a reflection on human needs, energy services, urban structures, social norms, and the role of policies to support the shift towards lower-energy societies. In recent years, a growing body of literature has been published on energy sufficiency in various disciplines. However, there has been limited exchanges and cooperation among researchers so far, hindering the visibility and impact of this research. This paper presents an assessment of where sufficiency research stands, especially in the perspective of policy-making. It is the first overview paper issued in the context of the newly-founded ENOUGH network - International network for sufficiency research & policy, established in 2017. In the first part, we provide a condensed literature review on energy sufficiency, based on dozens of recent references collected through the network. Through four main themes (the nature of sufficiency, the challenges of modelling it, the barriers to its diffusion, and the approaches to foster it), we summarise the key issues and approaches. We then present what the scholars themselves see as the priorities for future research, promising sufficiency policy options, and key barriers that research should help overcome. We collected their views through a questionnaire completed by more than 40 knowledgeable authors and experts from various disciplines. We finally build on the previous parts to draw some recommendations on how sufficiency research could increase its impact, notably in relation to policy-making.

The efficiency strategy to exploit the potential for energy savings in buildings still is applied rather slowly in most countries. In addition, there are indications that energy savings are partly compensated particularly by wealth but also rebound effects, the "empty nest" (persistence of elderly people and couples in family homes), and cohort effects (e.g. vintages of people or buildings). In Germany, as in other European countries, the existing trend in housing is a continuously growing floor space per capita. Over the last decades it expanded from about 20 m2 in 1960 to currently 45 m2 per person. Forecasts expect a further increase to more than 50 m2 per person. Obviously, more floor space needs more energy for space heating and cooling, ventilation, and lighting, but it also allows the household to operate more and or bigger appliances, all of which increase energy consumption. On the other hand, housing projects emerge offering relatively small private living spaces in combination with various shared spaces to use. Many of them are based on private initiatives. But what is the motivation behind it? And is there a higher need for new living concepts in the future? The proposed paper presents main drivers of increasing floor space per capita in Germany and discusses the question if more space is necessary for higher comfort. It presents different examples of housing concepts that strive to achieve good living with less space and suggests a "building typology of sufficiency". Finally, the paper discusses qualitatively to which extent these housing concepts can lead to less energy use and emissions. In this way sufficiency could be best friend with efficiency and tackle wealth, rebound, and other effects that counter-act efficiency progress. But therefore, as the paper concludes, politics and policies should recognise sufficiency as a field of action instead of referring to individual decisions and lifestyles.

Many European city governments have voluntarily committed to ambitious CO2-emission reduction targets until 2020 and 2050. Supported by dedicated structures and networks (e.g. Covenant of Mayors), local governments have already developed, or are currently developing, ambitious climate action plans, all pursuing the aim of radical CO2-emission reduction in the long term. Though, the development of climate action plans is only a first step, as the actual crucial and more challenging part its implementation. Besides financial investments also additional capacities, improved institutional structures and innovative strategies are necessary to successfully implement ambitious policies within existing national and regional framework conditions. There is often more competition than co-operation between cities. However, exchanging on common challenges in order to find new solutions provides potential for innovative ideas and new views on own structures. In particular, methods and formats for self-assessment and mutual learning can support cities' stakeholders to overcome their implementation gap in local energy and climate policies. This paper will present results from the first phase of the three year project "CASCADE", which was initiated by 19 European cities in co-operation with EUROCITIES. Within the project, implementation challenges are being addressed in an intensive process of self-assessment and mutual learning. The methodological "backbone" of this process is a qualitative benchmarking framework in the thematic fields of "Renewable energy sources and distributed energy generation", "Energy efficient buildings and districts" and “Energy in urban transport”. Up to a certain degree, existing local climate policy benchmarks provide a common exchange platform, but mainly for the comparison between cities. The CASCADE benchmarking framework goes beyond competitive comparisons. As a qualitative criteria-based assessment procedure it identifies key challenges and factors for a successful implementation of established local climate policy plans. These factors have been developed from a qualitative survey including interviews and workshops with representatives of the participating cities. Six cities serve as examples. Self-assessment reports were provided based on the CASCADE benchmarking framework focussing on the implementation status of their local climate policies. These reports were reevaluated by four or five project partners from different cities in a desk-review process. During subsequent four-days peer learning visits, the CASCADE benchmarking framework was used again as a tool for an in-depth assessment of the local climate and energy action plans and the local activities towards implementation of these strategic documents. Finally, the visitors drafted a feedback report with recommendations and improvements for the hosts. The paper describes the methodology of the CASCADE benchmarking framework for integrated learning, its applicability for peer learning processes, as well as first experiences and results from the peer learning visits.