NESO raises its November balancing-cost forecast to £439m; constraints are three-quarters of it

Serguey Asael Shinder16 October 2026, 14:123 min read

Great Britain's National Energy System Operator (NESO) has published its BSUoS forecast report for November 2026, the monthly outlook for the balancing costs that are recovered from network users through the Balancing Services Use of System charge. The headline: £439 million of balancing costs for November, 12% (£48 million) more than the £391 million NESO forecast on 21 September.

What moved the number. NESO attributes the change to a 10% (£30 million) increase in the constraints cost forecast and to a second component that rose 21% (£17 million). The share of demand expected to be met by renewables is unchanged at 44%. The bigger shift is in prices: the average wholesale electricity price assumed for November is now £152/MWh, 25% above the £121/MWh used in September, based on forward curves from 1–5 October. NESO gives a sensitivity: a consistent ±20% move in the forward curve would change the central forecast for the next 12 months by roughly ±9–13%. The report also notes that rising prices are beginning to feed into what generators bid to balance the system.

Constraints dominate. The six-month breakdown in the report makes the structure plain. For November, constraint costs are forecast at £336.8 million of the £438.6 million central total — about 77%. The remainder is small by comparison: frequency control £41.4 million, "other" £31.6 million, positive reserve £11.4 million, energy imbalance £10.4 million, restoration £6.0 million and negative reserve £1.0 million. The pattern holds across the winter: constraints are forecast at £290.4 million in December, £258.4 million in January, £276.3 million in February and £258.2 million in March. NESO explains that its constraint model was updated in March 2026 with new boundary limits from the Year-Ahead plan, and that many limits are lower because of a challenging outage plan needed for the Transmission Owners to maintain and upgrade their networks — which raises forecast constraint costs.

What users actually pay — for now. Since 1 April 2023 BSUoS has been a fixed tariff, so the forecast does not change today's bills directly. The published final tariff for October 2026 to March 2027 is £12.49/MWh. Against that, NESO's central estimate of the underlying cost is £20.43/MWh for November and £21.55/MWh for October. The gap shows up in the indicative forecast tariffs: £27.06/MWh for April–September 2027 and £21.45/MWh for October 2027–March 2028, with a carried-forward under-recovery of around £131–135 million a month in the first of those periods. NESO stresses that forecast tariffs are highly indicative until final tariffs are published in December.

Reading it. The report's own numbers say that in GB the cost of balancing this winter is, above all, the cost of moving power across a network with outages on it; wholesale prices widen the range, but constraints set the level. With a fixed tariff at £12.49 and an estimated cost above £20, the open question the report leaves is how much of this winter arrives in the April 2027 tariff.

Source: NESO, "BSUoS Forecast Report – November 2026" — https://www.neso.energy/bsuos-forecast-report-november-2026