Comment by Jon Saltmarsh, CTO at Energy Systems Catapult

At its simplest, energy flexibility means shifting when and how electricity is used or generated to better match supply and demand within grid constraints. Instead of power stations adjusting their output to follow demand – as they always have with fossil fuels – the future system relies on millions of smaller assets responding dynamically to system needs.

These assets are part of everyday life. Electric vehicles (EVs), heat pumps, home batteries, smart appliances and commercial energy systems all have the potential to flex their behaviour in response to control signals. On their own, each device makes a small difference. Together, they form a powerful, distributed resource.

Top-down becoming bottom-up

To understand how flexibility works, it helps to start at the top of the system. The National Energy System Operator (NESO) is responsible for balancing electricity supply and demand across Britain in real time. If demand begins to outstrip supply, for example on a cold, still winter evening, NESO must act quickly to keep the system stable.

Historically, this balancing act relied on fossil fuel generators ramping up output. But in a decarbonised system, flexibility comes from distributed sources. For example, instead of turning on another gas power plant, the system – operating within local network constraints – might draw on stored energy in batteries, shift EV charging to a later time or temporarily reduce demand from industrial users.

This is where flexibility markets and service providers come in. Organisations known as aggregators work by pooling together thousands of smaller assets – from homes, businesses and fleets – and managing them as a unified flexible resource. When the system needs support, aggregators send signals to participating assets to adjust their behaviour.

For example, a home battery might discharge electricity back into the grid for a short period. An EV charger might pause charging for 30 minutes. A heat pump might pre-heat a home slightly earlier when renewable energy is abundant, reducing demand later in the evening peak.

These changes are designed to be small and often unnoticeable to consumers. But, when they’re coordinated across thousands of assets, they can deliver significant system benefits, reducing strain on networks, lowering balancing costs and enabling renewable generation to be used more efficiently and cost-effectively.

Orchestrating flexibility

Signals that trigger this flexibility can come from different places. Some are operational, issued directly by system operators to maintain stability. Others are market-based, driven by price signals such as time-of-use tariffs that encourage consumers to use electricity when it is cheaper and greener.

Behind the scenes, digital technology plays a critical role. Data platforms monitor system conditions, forecast demand and generation, and optimise how flexibility is deployed ensuring networks do not become overloaded. Automation ensures responses happen quickly and reliably, without manual intervention. As the number of connected assets grows, this digital coordination becomes even more important.

However, flexibility is also shaped by markets, regulation and consumer trust. Assets must meet qualification standards to participate. Commercial arrangements determine how value is shared. Consumers need confidence that automated decisions will not affect comfort or control.

This is why scaling flexibility is as much a systems challenge as a technological one. It requires alignment between policy, market design, digital infrastructure and user experience.

Register your interest in GridFlex

What’s clear is that flexibility is becoming a foundational capability of the modern energy system. It enables renewables to operate more efficiently, reduces the need for costly infrastructure upgrades and creates new opportunities for consumers and innovators alike.

As millions of distributed assets connect to the grid over the coming decade, flexibility will move from emerging practice to everyday reality, quietly working in the background to keep the lights on in a cleaner, smarter future.

If you think your technology could support energy flexibility, you can find out more about the GridFlex programme and register your interest here.