UK Grid Warns Record Low Power Use to Test Network This Summer

(Bloomberg) -- The UK’s electricity grid operator is warning that power demand could reach record low levels this summer when solar generation overwhelms the grid.

Britain’s National Energy System Operator is expecting it may need to issue warnings to the market when there’s too much supply and not enough demand, according to a report about the summer outlook published Wednesday. These warnings happen a couple of times each winter but are rare in the summer.

The UK wants to expand renewable capacity to achieve an almost totally clean grid by the end of the decade. Most solar generation in Britain and smaller wind farms are connected to local networks not owned or controlled by NESO and the report highlights the complexity and cost of managing a network that relies heavily on intermittent renewable sources. 

“One of the great engineering challenges of decarbonisation is managing our system when there is lower demand coinciding with higher levels of generation from renewable sources,” Deborah Petterson, director of resilience and emergency management at NESO, said in a statement.  

The late May bank holiday has the greatest probability of extremely low demand but the lowest day could occur on any weekend between early May and late August, according to the report.

The situation will be more difficult this summer as there are set to be a number of pumped hydro plants shut off for maintenance, reducing a key way of creating demand - by pumping water up a hill or mountain. 

Winter periods have increasingly becomes times of stress for the UK’s grid. Earlier this year, the grid operator issued a warning to procure extra generation to ensure supplies were more than sufficient to meet demand during a period of low wind speeds. This summer will test the grid in the opposite direction. 

NESO expects that the grid could break a Covid-era record for low demand this summer. There’s now a 50% probability that demand will be below the previous record of 13.4 gigawatts, it said in the report. 

Solar has been particularly strong this year. The UK has already broken the record for maximum power generation from the sun ahead of the peak season in June or July. 

The influx of green power means that wholesale costs are falling. In Europe, the rapidly growing fleet has sent prices far below zero during some hours. 

Britain will benefit from the abundance of solar power generation on the continent, with export of cheap electricity supplies to the UK during the sunniest hours of the day. But that could also cause problems for the grid operator. 

The UK is linked to Europe via a variety of subsea interconnectors that send electricity to whichever market has the higher price. Even when the UK has more power than it can consume this summer, those price signals could mean that a European market flooded with cheap solar electricity is exporting to Britain. That would require the grid operator to intervene to alter the flow of power. 

©2025 Bloomberg L.P.