NESO explains its two Emergency Assistance calls: network constraints, not a lack of power
Serguey Asael Shinder2 min readGreat Britain's National Energy System Operator (NESO) published an explanation on 14 October 2026 of two Emergency Assistance requests it issued over the previous week. Its main message: the system had not run out of electricity — transmission constraints stopped available power from reaching the south.
What Emergency Assistance is. NESO describes it as an established, precautionary tool used by its control room and by other system operators for days when the margin is thinner than forecast. Using it, NESO stresses, is not a sign that supply was lost or that customers were about to be cut off. NESO also notes that it does not own power stations, transmission infrastructure or interconnectors and operates the system with the capacity available on the day.
Friday. NESO says it expected net imports to fall by around 700 MW: exports reduced power in the south by 1,200 MW while imports in the north rose by about 500 MW. That left a need for roughly 400 MW more power in the south, and network constraints prevented moving enough of the electricity being produced in the north. The control room instructed all the generation the market could make available in the affected area — about 400 MW of generation and batteries at full output. Then wind output fell quickly, by around 20 MW a minute, and system frequency dropped further than NESO would have liked, though it stayed above the statutory limit. The control room temporarily ran parts of the network above normal constraint limits while reassessing them in real time, and requested Emergency Assistance from France, which added power in the south, helped restore frequency and reduced flows across the constrained network.
Monday. This time the challenge was the network itself. Transmission infrastructure in the South East that had been expected back in service did not return — something NESO says was outside its control — which cut the amount of electricity that could flow into the region. Generation was available elsewhere, but not enough could reach London and the surrounding area. NESO requested Emergency Assistance on an interconnector, starting at 700 MW; as demand rose and the constraint continued, a further 500 MW was needed to keep transmission assets within normal operating limits, bringing the total to 1,200 MW.
NESO calls such requests relatively uncommon and says that is why the capability is valuable.
Source: NESO, explainer on its Emergency Assistance requests — https://www.neso.energy/news/emergency-assistance-what-it-and-why-we-used-it-over-last-week