The changing role of gas in the UK’s power mix

Why gas?

The government has a target to reach ‘clean power’ by 2030. In practice, according to the government’s Clean Power Action Plan this may mean that less than 5% of generation will come from unabated natural gas. Almost all, including the government’s, forecasts agree that even as we phase out gas from the bulk of our power system in terms of MWh’s, to ensure security of supply, we need to maintain roughly the same amount of gas capacity (MW’s) on the system in the early 2030s as we have today.

In their recent Future Energy Scenarios ‘10 Year Forecast’ the National Energy System Operator (NESO) forecast around 37 GW of gas in 2030, with a range of 46-32 GW.

RWE Image — Chart source: NESO, Future Energy Scenarios 2025, low-high range across all scenarios. *Capacity includes Gas CCGT, CHP, OCGT, gas reciprocating engines and CCS.

Why does the UK’s gas fleet continue to be critical?

1.Second-by-second, minute-by-minute – System services: Electricity systems are complicated: from the physics of keeping voltage and current in balance, to the matching of supply and demand for power in real-time every second of the day.

Within this hidden world that keeps modern society moving, thermal generation such as gas plays an important role in providing not just power when it is needed, but also what is known as ‘system services’, such as inertia.

The fact that a thermal plant ‘spins’ means that these large chunks of rotating metal effectively hold energy that can be used for stability. You can think of this as how a large ship keeps moving steadily through waves (high inertia), while a dinghy rocks violently with every ripple (low inertia). In the worst case, the dinghy capsizes - like a grid blackout when frequency swings too fast.

Thermal generation such as gas currently provides this service effectively ‘free of charge’. Whilst in the future other technologies such as batteries and synchronous compensators can be paid to provide a close substitute in the form of ‘artificial inertia’ (meaning they respond in milliseconds to changes in the grid), removing too much thermal generation too fast could increase the risk of fluctuations in supply and demand -causing instability on the electricity grid, potentially disrupting supply. Further detail on some of the other services that gas and other thermal technologies can provide is given in our recent article here.

2. Days, weeks and months - The Dunkelflaute: Translating to English as ‘Dark Doldrums’, this German word refers to periods caused by high-pressure weather systems that deliver low wind speeds and cloudy overcast conditions that limit wind and solar generation.

Dunkelflaute can last from a few hours to weeks on end, as illustrated here. This means that, even though storage, like batteries or pumped hydro, can be great for keeping the system supplied for up to a few hours and ‘softening’ the impact of a Dunkelflaute, their limited store of electricity will often run out within a matter of hours, necessitating a form of flexible generation that is able to operate without time constraints. Effectively, in this instance, gas steps in as an ‘insurance policy’ to keep the power system going.

Firm flexible back-up still matters

When most of our gas power stations were built, they were intended to run baseload - i.e. almost constantly for long periods of time, with a predictable pattern. However, as gas looks to provide the backstop for renewables, its use case will change:

Gas generations will run more intermittently, starting up and shutting down multiple times in a day.
For long-periods of time gas won’t be needed, for example in the summer months. Yet, whilst effectively sitting idle, it must remain ready to perform at a moment’s notice.
Run patterns will be unpredictable but nonetheless highly important, driven by uncertain weather events or ‘black-swan’ events.

These changes will make future operational and investment decisions around a gas plant much more complicated.

The hidden complexities of running less, but remaining ready

As gas assets run less often, the complexity of their operation and maintenance will increase, as will the financial decisions around them. This reflects the greater variability and lower predictability in future running patterns. Some of the key factors that need to be considered include:

1. Increased wear and tear from shorter runs.

Thermal cycling, i.e. starting up and shutting down, can potentially put more strain on some components. We can monitor and manage this with regular, targeted maintenance work, to maintain plant integrity and ensure our fleet remains reliable when called upon.
2. Plant preservation and reliability whilst sitting idle for long periods.

If gas plants sit idle for periods of time, a series of actions may be required to preserve the plant. For instance, after a plant has been off for two to three days the boiler may be drained or capped with nitrogen to avoid corrosion and maintain plant integrity. After 28 days, the whole boiler may need to be drained and dehumidifiers fitted to ensure no water remains, in order to minimise risk of corrosion. When starting up again, the plant will then need boiler re-filling and warming up before being tested to ensure it can reliably give the support the grid needs. An effective program of preventative maintenance is therefore critical.
3. Making investment decisions.

Plant maintenance is dictated by running hours and numbers of starts and stops on a gas unit. Generally speaking, a CCGT will require a service every 8,000 hours, and every 24,000 hours and / or 800 starts, a major outage is required (called a ‘c-inspection’). In the past, when gas plants operated more predictably, maintenance planning was straightforward - if a component had 8,000 hours left and the plant ran around 4,000 hours per year, a service could be confidently scheduled within two years.

In the future, as renewables dominate and gas units run far less (perhaps only 1,000 hours a year), that same part might last a decade. But if renewable build-out slows or demand increases unexpectedly, those hours could be used up far sooner. With long supply-chain lead times, operators must decide whether to invest early to retain flexibility to run more in future, or delay investment, reducing costs but risking early wear-out.
4. Labour and supply chain.

When industries are labelled as “declining,” investment dries up, fewer people train for careers in them, and supply chains weaken. There is therefore a danger that, if gas generation is interpreted as having no long-term role, we put at risk the future supply of both human and physical capital.

Crucially, the same people, skills, and industrial capacity that sustain gas assets today will be at the heart of tomorrow’s low-carbon solutions, from hydrogen-ready turbines to carbon capture. It’s therefore important that we maintain a positive and balanced narrative on the ongoing role of gas - so we can protect jobs, safeguard supply chains, and ensure a just transition that builds on existing expertise rather than letting it fade away.

How can policy and market frameworks best reflect the changing role of gas?

The UK led the way in moving from coal to gas before any other major economy, and our well-developed network of gas-fired power stations and supporting infrastructure will remain important for years to come. As the UK transitions to a decarbonised power system, gas will remain a vital part of the mix - running less often but when it does, it will matter more than ever. Gas therefore goes ‘hand in hand’ with a renewables-dominated power system – i.e., they are two sides of the same coin. Having reliable gas capacity available to support renewables and keep the lights on cost-effectively is a key strength of the UK’s power system.

However, as we’ve set out in this article, this evolving role will require us to change the way we operate and manage our gas assets. We face operational and investment decisions under increasing uncertainty and complexity. With over two decades of experience, RWE is well-placed to manage this transition efficiently and cost-effectively, having acquired a wealth of learning and technical know-how during this time.

We’re extremely proud of the efficient gas power stations we operate across the UK - and even prouder of the dedicated people who help keep them running reliably. Recognising and rewarding the important role existing gas assets play in delivering a low-cost, renewables-led power system is key to ensuring we continue to attract and retain a skilled industrial workforce.

The policy and market frameworks that underpin gas generation will need to evolve. A market-based approach remains essential to ensure firm, dispatchable capacity is retained at best value for consumers. In our next article in this series, we’ll explore what this should look like and how – in practice – we build a future-proofed market that delivers a secure and affordable energy system.

Executive summary

Gas remains essential in the UK’s energy transition: As we move towards a renewables-dominated clean power system, gas-fired generation will continue to play a critical supporting role. Gas plants will operate less frequently, but their flexibility and reliability are vital for maintaining system security and balance.
System services and security: Gas provides essential services such as inertia and frequency response, which are crucial for grid stability. Even as the share of gas in total generation declines, maintaining sufficient thermal gas capacity is necessary to support renewables and prevent supply disruptions during extended periods of low wind and sun (‘Dunkelflaute’).
Changing operational patterns: Gas plants will run more intermittently, with unpredictable patterns and longer idle periods. This potentially puts increased strain on the plants with more frequent starts and stops and requires robust maintenance and investment strategies to ensure readiness and reliability.
Expertise: As gas plants shift from baseload to more intermittent, flexible operation, the way in which we manage and maintain these assets must change. RWE’s extensive experience over two decades as an investor and operator of gas-fired power stations, positions us well to do this.
Workforce and supply chain considerations: Sustaining a skilled workforce and resilient supply chains is critical, as the same expertise will underpin future low-carbon solutions such as hydrogen-ready turbines and carbon capture. A positive narrative around the ongoing role of gas is therefore important.
Policy and market evolution needed: The evolving role of gas requires policy and market frameworks to ensure that firm, flexible capacity is retained at best value for consumers. We advocate for a market-based approach and will address these themes in a future article.

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