TECH

Hot and cold climate extremes push UK’s energy system to its limits, new report reveals

The arrival of cooler weather following a summer of heatwaves, is a timely reminder that the UK electricity system must be resilient to the effects of temperature extremes at both ends of the thermometer.

The Royal Meteorological Society has released a new report that highlights how recent weather conditions have influenced electricity generation, demand and the infrastructure that connects them.

Authored by experts from the society, the Met Office and multiple UK universities, the State of the Climate for the UK Energy Sector Report 2025-26 shows that more energy is being provided by weather-dependent renewable sources. But high and low temperatures will continue to put the energy grid’s capacity and infrastructure to the test.

Data from the National Energy System Operator (Neso) shows that renewable energy formed a higher percentage of overall energy generated in the UK over the reporting period (April 2025 – March 2026) than any other year on record. The proportion coming from the combination of solar and wind increased, providing more than 38% of the nation’s electricity. The proportion of gas-powered generation reduced to 25%.

However, the report highlights how extreme weather tests the resilience of the grid. The conditions that lead to very high and low temperatures create different challenges through increasing electricity demand, limiting generation and damaging network infrastructure. The UK’s energy network is having to adapt to cope with increasingly extreme temperatures. In cold conditions, the network is put under strain due to increased heating demand. This requires more energy at short notice, increasing reliance on non-renewable sources.

For those responsible for balancing the electricity system, including Neso, these weather extremes can create operational challenges. This makes it harder to match energy supply with demand.

In early January 2026, strong northerly winds brought cold Arctic air, snow and ice into large parts of the UK. Initially these winds provided up to 20 gigawatts (GW) of power towards the system, a significant proportion of the demand.

But as the freeze reached its peak on the evening of January 6, the wind died down and wind generation fell to less than a quarter of the levels seen in the preceding days. Simultaneously, electricity demand peaked, with the increase in heating needs seeing demand peak an additional 5GW higher than the previous day.

Electricity supply and demand have to be kept in balance in real time. When demand rises or available generation falls, the energy system operator can maintain that balance by using additional generators to increase their output, for example. On this occasion, gas-powered electrical generation filled the gap by providing more than 25GW to the system at it’s peak.

This meant the demand was comfortably met, but this was an expensive strategy that meant the operator was paying up to £700 per megawatt-hour (MWh) for this generation. This was due to the higher cost of turning to gas generation, and the need for additional generation at short notice which costs more than generation that can be planned further in advance. This compares to the usual rate of just over £100 per MWh for the rest of January.

At the other end of the spectrum, hot temperatures are increasingly becoming more of a concern for the sector.

The summer of 2025 was the warmest on record at the time, with temperatures 1.51°C higher than average. During warmer temperatures, the network operator often limits the amount of power that transmission lines carry around the country to prevent components overheating. This reduces the risk of lines expanding more with heat which would make them sag and potentially short out on nearby vegetation or structures beneath.

Nevertheless, several faults in the network were attributed to heat causing infrastructure damage, leading to power cuts across parts of England, especially during two periods of heatwaves that occurred at the end of June and start of July.

In Europe, where temperatures also spiked, nuclear power plants were forced to limit output or shut down altogether because the water used to cool them with, taken from nearby rivers, was too warm. Increased temperatures and below-average rainfall also increased fire risks. The largest area lost to wildfire burning in the UK since satellite records began included a “mega-fire” in Scotland. Several of these fires led to localised power cuts across the country.

Preparing for future extremes...The UK’s new grid upgrade plan from the government, which aims to expand and modernise the British grid system to allow for connections to new generation sources and upgrades of current infrastructure, needs to consider the consequences of extreme temperatures. This includes ensuring that upgraded infrastructure can withstand the extreme heat we are now seeing more regularly in UK summers, as well as ensuring that capacity for transmission of electricity from generation sources to population centres is increased.

Delays to electricity grid upgrades risk higher consumer bills as the operator is required to pay wind farms to stop generating because electricity produced cannot be be carried to where it is needed, replacing it with more local gas-powered generation instead.

The resilience of the UK grid has stood up well to the challenges it faced from the weather in the past year. But maintaining that resilience requires continued investment and adaptation as the climate, energy needs of the nation and profile of energy generation all continue to change.

The Royal Meteorological Society’s annual report has revealed that extreme heat and cold are pushing the UK’s energy system to its limits. The document highlights the severe impact these temperature fluctuations have on energy infrastructure and underscores the urgent need to modernize the sector.

Key impacts on the energy system:

• Transmission constraints due to heat: During heatwaves, the grid operator must limit the amount of electricity flowing through transmission lines to prevent components from overheating. Heat causes cables to expand and sag, creating a risk of short circuits should they come into contact with vegetation.

• Localized blackouts and fires: The summer of 2025 saw temperatures 1.51°C above average. Extreme heat caused physical damage to infrastructure and triggered wildfires—including a "mega-fire" in Scotland—resulting in localized power outages across parts of England.

• Challenges for European nuclear power generation: Extreme heat also forced nuclear power plants in continental Europe to reduce output or shut down entirely, as the river water used for cooling had become too warm.

• Higher costs for consumers: Due to delays in upgrading the transmission grid, the operator is frequently forced to pay wind farms to halt clean energy production—since the power cannot be transported—and replace it with energy from local gas-fired plants, which drives up electricity bills.

Adaptation plans and requirements: The British government’s new grid upgrade plan faces the challenge of ensuring that modernized infrastructure can withstand frequent extreme heat, while also providing greater capacity to transport electricity from new generation sources to urban centers. The regulatory body Ofgem has also launched investigations to assess the performance of the market and the electrical system—managed by the NESO—during recent heat spikes.

Royal Meteorological Society