The Grid in Focus
№ 02 · Balancing Costs · FY 2024/25
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£1.7 billion to turn wind farms off.

In the financial year just ended, NESO spent more on managing transmission constraints — paying generators in the wrong place to turn off, and others in the right place to turn on — than the entire cost of balancing Britain's grid as recently as 2018. That single line item is now bigger than the rest of balancing put together.

— Constraint costs, FY 2024/25
£0.0bn
Up 64% in a single year — driven by record wind output meeting a transmission network that physically cannot move it from Scotland to England. Total balancing cost: £2.7bn.
Total balancing cost
£0.0bn
FY 2024/25, +10% YoY
Constraint share
0%
of total balancing spend
Wind curtailed
0TWh
+81% YoY thermal constraint volume
Projected by 2030
£4–8bn
NESO's own forecast range
Figure 01

The seven-year trajectory

Annual balancing cost since 2018/19. The 2022/23 spike was the gas-price crisis; the 2024/25 rebound is something different — a structural problem. As more wind connects in Scotland and the wires south stay the same size, costs rise even when wholesale prices fall. Hover any bar for the full breakdown.

The signal in the noise
Constraint payments aren't a sign of mismanagement. They're the predictable, accounting-line cost of building wind faster than the wires that move it. Every £ of constraint cost is a £ of stranded clean energy — and a £ that could have been a transmission upgrade five years earlier.
Figure 02

Where the £2.7 billion went

Composition of FY 2024/25 balancing spend, using NESO's published cost categories. Constraints dwarf everything else — they're now nearly twice the size of the next-largest category. Hover any bar to explore.

Figure 03

Constraints alone are now bigger than total balancing was in 2018

A direct comparison. The orange bar — money paid in 2024/25 to not generate, or to compensate for those who didn't — exceeds the entire balancing budget from six years earlier. This is what scaling a grid faster than its bones can carry actually looks like in pounds.

Source. Figures from NESO's 2025 Annual Balancing Costs Report and the Monthly Balancing Services Summary on the NESO Data Portal. Category breakdown for FY 2024/25 is approximate, derived from the Annual Report's stated totals and historical proportions; the MBSS data files contain the definitive month-by-month split. Method. Categories follow NESO's published taxonomy (Constraints, Reserve, Response, Energy Imbalance, Reactive, Restoration, Minor Components). The 2030 projection range is from NESO's May 2024 Annual Balancing Costs Report and Future Projections.
The Grid in Focus
Liam Jack — Energy Networks