Britain’s grid operator has issued a second emergency call this week for power plants to crank up output, as a record-breaking heatwave puts the electricity system under strain.
The National Energy System Operator (Neso) sent the alert at 11.30pm on Thursday, asking generators to ‘make any additional generation capacity they may have available’ for Friday evening. Supplies were expected to be tightest between 7pm and 10pm.
It is only the second time Neso has issued such an alert in summer. The first came last Tuesday night. These warnings, known as Electricity Margin Notices, are normally a winter tool when gas plants are pushed to fire up extra capacity. The Met Office has issued a red extreme heat warning covering parts of England and Wales, with temperatures forecast to hit 37C. The June maximum temperature record has provisionally been broken.
A Neso spokesman said: ‘Our forecasts are showing tight margins on the electricity system for Friday evening. This is due to the impact of extremely high temperatures affecting Great Britain and the Continent.’
The spokesman added: ‘An EMN has been issued to the market. This is a routine tool, and means we are asking market participants to make any additional generation capacity they may have available. The EMN does not mean electricity supply is at risk.’
The notice warned that a ‘maximum generation service may be instructed’, meaning power plants could be told to temporarily exceed their usual limits.
Tuesday’s alert was withdrawn after Neso bought roughly 1.7 GW of extra power from Europe through undersea cables. Reports put the cost of those emergency imports at around £10 million. British households and businesses will ultimately pay that bill through their energy charges.
At 7.30am on Friday, gas plants were meeting roughly 40% of Britain’s power needs. Solar was providing 10% and wind 19%, according to grid data.
Here is the awkward part. Soaring temperatures actually make solar panels less efficient, not more. Panel output drops by 0.3% to 0.5% for every degree above 25C at the panel’s surface. On a 35C-plus day, panels run far hotter than that. The hotter it gets, the less the panels deliver, just when demand from fans and air conditioning is at its highest. Gas plants are picking up the slack. Without them, the lights would already be in trouble.
The wider picture is that Britain has spent two decades closing reliable coal and gas capacity and replacing it with weather-dependent wind and solar. That has left the grid thinner, more reliant on imports through undersea cables, and more exposed to days like this one. When the sun beats down and the wind drops, the system has to scramble.
The cost of those scrambles falls on bill payers. Every time Neso pays a premium for emergency imports, or pays a gas plant to run harder, the money comes from consumers. The Bank of England’s years of cheap money and the government’s net zero spending commitments, paid for by taxpayers and bill payers, have done nothing to fix the underlying problem: not enough firm, reliable generation on British soil.
Neso said it would review the situation again on Friday morning and update the market. No blackouts have been reported.
