Overview
- The National Energy System Operator (Neso) issued an electricity margin notice covering 7pm–10pm on Wednesday June 24, signalling that system margins are forecast to be tight for that evening.
- The notice is a routine market signal that asks suppliers to make additional capacity available and does not mean electricity supply is immediately at risk.
- Forecasters expect a western‑Europe heat dome to push temperatures toward 40°C in parts of England and Wales, which will increase use of fans and air conditioning and raise peak electricity demand.
- Very high temperatures and low wind also reduce generation and cooling efficiency at plants that use water cooling and at some gas and nuclear units, which adds pressure to the system.
- Issuing a margin notice in summer is uncommon and could lead to knock‑on impacts if conditions worsen, so markets, operators and commuters are watching supplier responses and weather alerts for any further escalation.