Power systems worldwide are entering a fundamentally different operating regime defined by rapid electrification, accelerating renewable deployment, and volatile fuel markets. The Carbon Trust argues that energy system flexibility is no longer a technical optimisation but a strategic enabler of affordability and security. This ‘invisible infrastructure’ is essential for systems designed for variability rather than predictability. Countries that embed flexibility early can significantly reduce system costs; in Great Britain, a fully flexible energy system is estimated to deliver net savings of £9.6–£16.7 billion per year by 2050.

The ‘build more’ approach is often misguided

Traditional responses to rising electricity demand typically involve building physical infrastructure like new generation and network capacity. However, this approach is increasingly inefficient and slow for renewable-led systems. High shares of variable renewables shift system value toward balancing and responsiveness. Flexibility allows systems to make better use of existing assets, reducing the need for over-build while maintaining reliability. In Great Britain, network flexibility delivered an estimated £300 million in savings for billpayers in 2024, with projections of over £3 billion in savings between 2025 and 2027.

Guidance is fragmented and gaps persist

Despite the clear case for flexibility, international guidance often stops short of providing investable economic cases. To address this, the narrative must focus on system-level cost, security, and reliability outcomes rather than individual technologies. Lessons from mature systems, such as the UK, demonstrate that explicitly addressing trade-offs and sequencing is vital to ensure flexibility delivers its full value rather than underperforming.

What is flexibility? Definitions matter

Flexibility is defined as a suite of operational decisions, market readiness, and digitally-led services that transform static operations into a dynamic system capable of absorbing pressures. It operates across the entire power system, including generation, demand-side management, storage, and sector coupling like electric vehicles and hydrogen gas. Policymakers must distinguish between progressive flexibility aligned with Net Zero pathways and transitional responses that may lock in fossil fuel dependence.

Building the economic case catalyses implementation

Flexibility delivers the greatest value once renewable penetration begins to strain networks but before infrastructure over-build is locked in. Acting early allows for the deferral or avoidance of unnecessary investment. Flexibility drives down overall costs by mitigating network constraints and avoiding the curtailment of renewable energy, thereby maximising the utilisation of existing infrastructure and limiting wasted energy.

UK flexibility impacts in 2024

The UK provides evidence of the tangible impacts of flexibility. In 2024, the system achieved 9 GW of contracted capacity and 22 GWh of dispatched services, resulting in USD 383 million in billpayer savings. This progress illustrates how flexibility can move from a technical niche to a core component of national infrastructure.

Energy security

Flexibility enhances energy security by reducing exposure to imported fuels through the maximisation of domestic renewable generation. This has become particularly salient following recent global fuel price volatility, as flexible systems are better able to absorb economic shocks.

System reliability

Reliability is maintained through fast response and controllability without relying solely on high-cost, low-utilisation backup generation. Demand response and storage are used to manage stress events and reduce operational risks associated with increasing variable renewable energy.

Without clear value, flexibility will remain a contingency and not a system enabler

Too often, flexibility is treated as a fallback rather than a core design principle. This framing results in under-investment and a default to infrastructure-heavy solutions. Projections show that short-term flexibility requirements will rise significantly by 2035 across all economies, with the largest growth expected in emerging and developing economies under both current policy and Net Zero scenarios.

Determining and modelling the value of flexibility is therefore a critical enabler of implementation

Holistic assessment reveals that flexibility benefits accrue across generation, networks, and demand. The costs of failing to implement flexibility are already high; the IEA reports that grid congestion cost almost USD 8 billion in the United States and USD 4.5 billion in the EU in 2024. Furthermore, renewable curtailment in the EU exceeded 10 TWh in 2024. Embedding flexibility into system modelling and cost-benefit analysis is essential to reveal its contribution to affordability and security.

Drive change where markets need it most

In vertically integrated systems where generation and networks are operated by the same institutions, flexibility may not emerge without deliberate intervention. Modelling the value of flexibility provides an evidence base for planners to compare it directly against conventional build-out options, revealing where optimisation can defer costly infrastructure while maintaining security.

Flexibility will not scale on intent alone. It must be driven by policy

Power systems are under strain due to a lack of flexibility, not necessarily a lack of capacity. The report recommends three immediate actions: make flexibility visible by quantifying its system-wide value; design for flexibility by embedding it into planning and regulatory frameworks as a core principle; and target binding constraints such as peak demand and congestion where flexibility delivers the highest value.