UK grid operator issues heatwave warning over power supplies

Britain's National Energy System Operator (Neso) has issued a new heatwave warning, cautioning that electricity supplies could be affected as extreme temperatures place unprecedented strain on the grid.

Unusual Summer Pressure

While summer typically places less stress on the power grid, this week's heatwave is expected to bring "extreme temperatures" that could impact electricity supply on Thursday evening. The surge in demand is driven by households using fans and air conditioning, creating record pressure on the system.

Neso issued a rare overnight notice calling on energy companies to provide additional supply to meet cooling demand. This marks the third heatwave in the UK this summer and the second warning from Neso in two months.

Previous Incidents

During a heatwave in June, when temperatures reached a record 37.7°C, the organisation was forced to request additional power.

Supply Gap and Response

According to Neso, the UK grid faces a supply shortfall of approximately 1.2 gigawatts during peak evening demand. The organisation stated it is "giving participants the opportunity to offer any additional generation or flexibility during the period under assessment."

Neso added: "Our forecasts show that margins are tight during the peak period tomorrow evening (Thursday). This is due to extreme temperatures across Europe, which have reduced the availability of some generation."

Climate Change Reshapes Grid Challenges

The warning signals a reversal of traditional pressure patterns on the UK's energy system. Historically, winter heating demand placed the greatest strain on the grid. However, rising summer temperatures have increased the use of air conditioning and fans, making pressure a year-round phenomenon.

Supply Constraints

Increased demand coincides with reduced supply. Low wind speeds have left many of the UK's wind farms idle, increasing reliance on domestic gas-fired power stations, nuclear plants, and costly energy imports.

According to National Grid's real-time data, wind power accounted for just 6.6% of the UK's electricity mix on Wednesday. During daylight hours, the country's growing number of solar farms helped compensate for the drop in turbine output. However, during the evening and night, the grid is forced to rely heavily on fossil fuels and expensive foreign energy from neighbouring countries.

European Context

Continental Europe is also experiencing a major heatwave, expected to intensify in the coming days. The UK depends on France for much of its emergency electricity supply, but France has been forced to reduce output from several of its nuclear plants because nearby water sources are too warm to cool the reactors.

No Immediate Blackout Risk

Neso added that the warning does not signal an imminent series of power cuts. Once buffer capacity is secured, the organisation typically withdraws the warning, as occurred during the June heatwave last year.