Reflections on solar panels. Photo by Henry & Co. on Unsplash

The fixity of flexibility

25 June, 2019

Peter J Forman

Elizabeth Shove

Reading time: 9 minutes

There is widespread agreement on the importance of flexibility in the energy sector, but what does it mean? Peter Forman and Elizabeth Shove explore three common interpretations.

There is widespread agreement about the importance of flexibility in the energy sector. But what does flexibility mean? In what follows, we identify three common interpretations. These include definitions of flexibility as a feature of whole energy systems; as a commodity that figures in energy markets; and as an outcome of specific interventions in supply or demand.

We suggest that all three interpretations rest on assumptions about the extent and character of energy demand and that some have the perverse consequence of fixing ideas about societal needs and limiting the forms of ‘flexibility’ that are discussed. As well as articulating some of the rigidities in debates about flexibility, we point towards a more ambitious agenda capable of engaging with significant changes concerning what energy is for and how it is provided.

Why is flexibility important?

There is nothing new about the challenge of matching energy demand and energy supply and of doing so in real time. What is new is the need to introduce more renewable – yet also more intermittent – sources of energy supply. The complication is that the times when renewable sources of power are most plentiful may not always match the times when that energy is needed. Currently, the majority of renewable energy resources are used to generate electricity. It is in this context that commentators argue for developing future electricity systems that are more flexible than those that exist today. In Ofgem’s words, there is now an ‘increasing need for greater flexibility across the power system, as we see more low carbon generation’ (Ofgem, 2017: 6). As this and many other such statements indicate, flexibility has become a priority within policy, industry and academic debates across the energy sector.

What is flexibility?

Despite widespread agreement that flexibility is important, there are different interpretations of what flexibility involves. There are three dominant, sometimes overlapping, discourses within the existing academic and grey literature.

1. Flexibility as a property of whole energy systems

Some think of flexibility as a measure of an energy system’s ability to ‘respond rapidly to large fluctuations in demand and supply’ (Chandler, 2008: 13). From this point of view, flexibility is a quality of whole energy systems (see, for example: IEA, 2018; Ofgem, 2017; Sanders et al., 2016). As might be expected, there have been numerous efforts to quantify the extent of the flexibility contained within whole energy systems. Usually, this involves adding up the total amount of energy that could be responsively generated, stored or deferred through different ‘flexibility technologies’, including forms of storage, demand-side response, international interconnectors, and fossil-fuel powered generators (Sanders et al., 2016). The resulting measurements, typically expressed as gigawatts of flexibility, make it possible to follow trends in energy systems over time and to compare the relative flexibilities of national energy systems. In relation to electricity in particular, increasing reliance on renewables has led to growing interest in flexibility and responsiveness, as distinct from the challenge of simply generating enough power to meet anticipated demand.

2. Flexibility as a commodity

For different actors in the energy system, including aggregators, market regulators and economists, flexibility figures as a commodity that can be bought and sold. In effect, flexibility refers to the potential to profit from the capacity to ramp supply up or down. It is in this context that phrases such as “3GW of new flexibility [has been] contracted since 2016” make sense (Ofgem, 2017: 6).

In the electricity sector, the markets for flexibility and for electricity itself are intertwined in that the value of flexibility is directly related to pressures on the relationship between supply and demand. It is also important to notice that flexibility is ‘used’ in different ways. For instance, storage capacity (using batteries) might be purchased by network arbitrage service providers who use it to ‘smooth’ load curves, minimising the peaks in demand that cause electricity prices to rise. The relative value of different forms of flexibility depends on these purposes and on related issues of scale (how much flexibility can be provided), reliability, and the speed at which providers can respond to fluctuations in the system.

Making a functioning market depends on consistently managing and representing the qualities of flexibility. In keeping with this aim, the UK’s ‘Smart Systems and Flexibility Plan’ seeks to modernise the UK electricity system’s regulatory environment to “open up new markets, improve coordination across the system and enable these businesses to realise the true value of their services” (Ofgem, 2017: 4).

3. Flexibility as an attribute of specific ‘solutions’

Methods of storing energy or of limiting demand at specific times represent instruments or techniques for increasing flexibility at different points in the energy system as a whole. There is currently real interest in specifying and evaluating the qualities of different ‘solutions’. For example, storage technologies such as battery systems, thermal energy storage and pumped hydro are often compared in terms of the number of gigawatts they can deliver and the amount of notice required before they can start to transfer that energy (Andrey et al. 2016). Issues of reliability are also important. Supply-side technologies are generally thought to be more reliable than their demand-side counterparts, which include methods of pricing and persuasion that are designed to encourage people to use energy at off-peak times. Flexibility providers consequently distinguish between demand-side measures that are focused on large institutions and those that are aimed at domestic consumers, whose actions are harder to ‘aggregate’ and manage at scale. In both cases, there is an often-implicit goal of simply shifting energy ‘needs’ across time, and of meeting, rather than modifying, what are taken to be fixed and ‘natural’ requirements (for instance, the ‘need’ for a daily shower). These assumptions run through current debates, appearing in statements such as those of Shakoor et al., who write about the scope for using ‘demand-side resources for system balancing to enhance system flexibility without compromising the service quality delivered to end customers” (Shakoor, Davies, & Strbac, 2017: 10 – our emphasis).

In short, discussions of flexibility are generally about finding ways of making greater use of renewable sources of supply whilst continuing to meet current patterns of demand and maintain contemporary societal rhythms. This goal is so widely taken for granted that people rarely consider more fundamental questions such as: ‘What actually is demand?’; ‘How has it emerged historically?’ and ‘How might it change in the future?’

What is flexible? What is fixed?

In most of the discussions we reviewed, there was almost no consideration of the basic contours of energy consumption, and no historical analysis of the fixity and flexibility of the services that energy makes possible. For example, rather than asking about how meanings of thermal comfort themselves evolve, judgements are made about more and less flexible means of delivering a given indoor climate. Sometimes changes are anticipated, but these are usually framed within a narrow range of possibilities. For instance, in considering the uptake of electric vehicles, authors such as Kaschub, Jochem and Fichtner (2016) describe the anticipated consequences that this development will have for energy demand. This is relevant work, but it supposes that journeys and destinations will remain largely unchanged and that electric vehicles will simply substitute for the combustion vehicles they replace.  There is no place here for thinking about the flexibility (or not) of mobility itself.

In putting questions about the longer-term trajectories of demand aside, discussions of flexibility have the unintended consequence of imagining and also ‘fixing’ a particular model of normality that is based on the present. Since technologies, measures and instruments such as storage and demand-side management are ‘performative’ (meaning that they have effects in the world), they have the unintended consequence of reproducing and stabilizing specific understandings of need and demand. As a result, they are likely to obstruct, rather than actively foster, a more fundamental transition in the flexibility of demand at a societal scale.

Reimagining flexibility

By focusing on means of meeting present needs, current discussions of flexibility ironically limit the imagination and impede the carbon reduction agenda. This is because they have the dual effect of a) reproducing interpretations of consumers’ needs, and b) obscuring the scope for a more challenging debate about the foundations of demand and how rigid or flexible this might be. In response, we argue for re-appropriating the language of flexibility and for developing and pursuing a much more ambitious agenda. For example, might changing practices and conventions themselves constitute sources of flexibility?

In the longer-run, making greater use of renewable energy and doing so as effectively as possible depends on reconfiguring the detail and timing of what people do. This might involve reintroducing seasonal variations in consumption and production or reconnecting societal and natural rhythms including those of heat and light. Similarly, and in so far as peaks in demand are a problem, there is scope for recognizing that these are not natural or inevitable: they are outcomes of the social organization of daily life – from morning commutes through to conventions about when to have an evening meal. Such arrangements are not fixed for all time but are always on the move – movements that are partly defined by systems and forms of energy provision, and by policy interventions of many kinds.

Seeing the possibilities for flexing social arrangements and for doing so at scale depends on overcoming the present fixities of flexibility . This is a necessary step in configuring patterns of demand that are, in and of themselves, better aligned with the complex rhythms of renewable energy supply.


  • Andrey, C.; Fournié, L.; Gabay, M.; de Sevin, H. (2016). The role and need of flexibility in 2030: focus on energy storage. Brussels.
  • Chandler, H. (2008). Empowering Variable Renewables. Paris.
  • Davison, P. (2018). Activating Community Engagement (ACE): Project Trial Analysis Report.
  • IEA. (2018). Energy Transitions in G20 Countries: Energy Transitions Towards Cleaner, More Flexible and Transparent Systems. Paris.
  • Kaschub, T., Jochem, P., & Fichtner, W. (2016). Solar energy storage in German households: profitability, load changes and flexibility. Energy Policy, 98: 520–532.
  • Ofgem. (2017). Upgrading Our Energy System: Smart systems and flexibility plan.
  • Regen SW. (2017). Sunshine Tariff Summary report.
  • Sanders, D., Hart, A., Ravishankar, M., & Brunert, J. (2016). An analysis of electricity system flexibility for Great Britain. London.
  • Shakoor, A., Davies, G., & Strbac, G. (2017). Roadmap for Flexibility Services to 2030. A Report to the Committee on Climate Change. London: Pöyry.
  • Sidebotham, L. (2015). CLNR Closedown Report.

Banner photo credit: Henry & Co. on Unsplash

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