Comment by Jon Saltmarsh, CTO at Energy Systems Catapult

When people talk about making our energy system smarter, they often reach for a familiar term: demand response. It’s a useful tool, but it’s only one piece of a much bigger picture.

We need to bust the myth that energy flexibility is only about reducing demand during peak periods when the grid is stretched. Flexibility is about shaping energy use to make the system more resilient, cost-effective and capable of integrating far higher levels of renewable generation.

Simply reducing energy flexibility to demand response risks missing the scale of the transformation required and the huge opportunity it presents for UK innovators.

From peak events to continuous optimisation

Traditional demand response tends to be event-based. The systems operator identifies a period of stress, like a cold winter evening, and calls on contracted assets to reduce demand or increase supply.

But the future system will not only provide support during isolated peak events. It must continuously manage variability from solar and wind, maintain electrified heat and transport demand within network constraints, and maintain stability across multiple timeframes – from seasons to seconds.

Flexibility, therefore, is no longer just a reactive tool deployed in moments of stress. It becomes a core operating principle of a renewables-powered system.

It’s not intervention, it’s infrastructure

Demand response and demand flexibility are, therefore, two separate approaches. It’s not just a semantic distinction – it reflects a fundamental shift in how the energy system operates.

Demand response is intervention based: a signal is issued, consumption is reduced, the event passes. Demand flexibility, by contrast, is embedded in the system itself. It shapes consumption patterns continuously – not only when the system is at its limit, but as a matter of routine operation.

Smart electric vehicle (EV) charging isn’t limited to responding during a single peak event. It optimises charging profiles to align with wind generation and network constraints. Heat pumps don’t just turn down during times of peak energy demand – they pre-heat homes when electricity is abundant and cheaper. Commercial refrigeration, industrial processes and building management systems increasingly adjust in response to dynamic price signals and system conditions.

This is not a series of isolated actions. It is coordinated optimisation across millions of connected assets.

Digitalisation makes this possible. Forecasting tools can anticipate renewable output, automated platforms can dispatch flexibility in real time and aggregators can combine thousands of small devices into resources that can participate in markets once reserved for large power stations. In this context, flexibility becomes infrastructure – as essential to system stability as transmission lines or substations.

A step change in the energy system

If energy flexibility were only about shaving peaks once or twice a year – reducing power consumption by businesses and consumers during peak periods – its strategic value would be limited. But research indicates that flexibility tools hold transformational economic and operational value for the UK’s energy transition.

New modelling published in early 2026 shows that flexibility could cut up to £125 billion from UK power system costs by 2050. That encompasses energy generation, network reinforcement, and the balancing and operating costs that the system incurs when demand and supply are out of sync.

These kinds of gains don’t come from peak shaving alone. They emerge when flexibility is integrated across electricity, heat and transport, and when digital and market systems enable assets – from EVs to heat pumps – to participate day-in, day-out. Achieving this requires innovation not just in devices, but in how systems communicate, forecast and coordinate in real time.

This is exactly the focus of projects such as GridFlex, a UK initiative led by Energy Systems Catapult in partnership with Digital Catapult. The GridFlex programme is exploring the technological and market enablers that will allow digital innovation to unlock flexibility more effectively and at scale, building frameworks and networks that support long-term growth in the flexibility ecosystem.

Treating flexibility as merely another form of demand response risks underestimating both its value and its necessity. Realising its full potential means designing markets, regulation and digital infrastructure around continuous optimisation, not isolated interventions.

Demand response will continue to play an important role. But if the UK is to build a cleaner, smarter and more cost-effective energy system, flexibility must be recognised for what it truly is: not just a tool for peak shaving, but a core design principle of the future energy system and a huge opportunity for UK innovators.

If you’re an innovator, industry partner or researcher who wants to be part of shaping the UK’s flexible energy future, you can register your interest in the GridFlex programme and stay informed about upcoming opportunities. Sign up here: https://www.digicatapult.org.uk/programmes/programme/gridflex/