UK flags tight power margin for Monday

Britain’s National Energy System Operator has warned that electricity supplies may be tight on Monday 28 September 2026, particularly during the evening peak. The operator issued a margin notice covering the period from 16:00 to 19:00 BST, highlighting that available reserves could fall below preferred levels during those hours.

The notice identifies a possible margin shortfall of about 1.4 gigawatts starting at 16:00. This potential gap reflects the difference between forecast demand and the buffer of spare generating capacity that operators aim to maintain for security of supply.

In response to the tight outlook, NESO has called on power generators to make more capacity available for the Monday evening period. The operator has also approached neighbouring countries to secure extra imports, adding another source of flexibility to help cover the anticipated margin.

Alongside supply-side actions, NESO has queried UK suppliers about options to reduce demand. Such measures can include incentivising lower consumption at peak times, helping to narrow or eliminate the forecast shortfall in reserves without affecting essential services.

Despite the warning of tight margins, NESO describes the margin notice as a routine, preventive operational step. The operator states that there is no risk to consumer electricity supplies and that Great Britain’s electricity system remains secure.

Margin notices are used to signal that additional capacity or demand flexibility is needed to maintain comfortable reserves. They are part of standard system operations and can be withdrawn if conditions improve before or during the affected period.

NESO indicates that a forecast increase in wind generation overnight should relieve pressure on the system after the evening peak. As wind output rises, it is expected to add to available capacity and rebuild reserve margins.

This anticipated change in weather-related generation suggests that the tight conditions are likely to be temporary, focused on the early evening hours before wind power strengthens later in the night.