The National Energy System Operator (NESO) has issued a warning about potential power supply shortages as a heatwave sweeps across Great Britain, driving electricity demand to near-record levels. The operator called on all available generators to maximize output and urged consumers to reduce non-essential electricity use during peak hours.
Heatwave Sparks Unprecedented Demand
Temperatures soared above 35°C in parts of England on Friday, prompting a surge in air conditioning and cooling system usage. NESO reported that electricity demand reached 38.2 gigawatts (GW) by mid-afternoon, approaching the all-time peak of 39.1 GW set during a cold snap in 2023. The operator stated that the grid is under significant strain, with limited spare capacity to cover unexpected outages.
In a statement, NESO said: “We are experiencing a period of very high electricity demand due to the extreme weather. We have issued a notice to the market asking for all available generation to be brought online and for demand-side response measures to be activated. We are working closely with National Grid to ensure the stability of the system.”
Multiple Factors Strain Supply
The warning comes as several factors coincide to reduce supply margins. A planned maintenance outage at the Sizewell B nuclear power plant has taken 1.2 GW offline, while low wind speeds have curtailed output from wind farms. In addition, two interconnectors linking the UK to France and Belgium are operating at reduced capacity due to technical faults.
Analysts at energy consultancy Cornwall Insight noted that the situation is reminiscent of the energy crisis in 2022, when tight margins led to emergency measures. However, they stressed that the current risk is lower due to increased battery storage capacity and demand-side flexibility.
Consumers Urged to Conserve
NESO has not yet declared a formal emergency, but it has escalated its market notices to the second-highest level, indicating a high risk of supply shortages. The operator is activating its Demand Flexibility Service, which pays businesses and households to reduce consumption during peak times. Participants are asked to shift usage of high-power appliances like washing machines and dishwashers to off-peak hours.
“Every kilowatt-hour saved helps reduce the risk of blackouts,” said a spokesperson for Energy UK, the trade association. “We encourage consumers to follow NESO’s guidance and be mindful of their electricity use, especially between 4pm and 8pm when demand is highest.”
Impact on Energy Prices
The supply crunch has already pushed wholesale electricity prices to levels not seen since early 2024. Day-ahead prices for Friday reached £250 per megawatt-hour (MWh), more than double the average for this time of year. The price spike is expected to feed through to household bills, though most consumers are on fixed tariffs that insulate them from short-term fluctuations.
The government has sought to reassure the public that there is no immediate threat to supply. A spokesperson for the Department for Energy Security and Net Zero said: “The UK has a resilient energy system, and NESO is taking all necessary steps to maintain security of supply. We are monitoring the situation closely and are in constant contact with grid operators.”
Long-Term Implications
The heatwave has reignited debate about the UK’s energy security as it transitions to net-zero emissions. Critics argue that the reliance on intermittent renewables and imported power leaves the grid vulnerable to extreme weather events. The government has defended its strategy, pointing to investments in battery storage, hydrogen, and new nuclear capacity.
NESO’s warning comes just weeks after it published a report outlining the need for more flexible generation capacity to manage summer peaks. The operator has called for accelerated deployment of new gas-fired power plants with carbon capture, as well as increased interconnection with European grids.
As the heatwave is forecast to continue into the weekend, NESO has warned that further notices may be issued if conditions worsen. The operator will continue to monitor the situation and update the market accordingly.
