03Where does power flow, and why do prices split?
Britain's wind is in the north, and it's paid to switch off
What does it cost Britain when its northern turbines produce more than the lines can move?
Britain keeps one national electricity price and pays generators, mostly Scottish wind, to switch off when the grid cannot move their power south.
Over the 55 months from April 2022 to October 2026, relieving these grid bottlenecks (thermal constraints: lines that would overheat if they carried more) cost about £7.6 billion, roughly £1.7 billion a year, by the count of NESO, Britain's grid operator.
The costliest month was September 2026, at about £474 million.
When the grid can't carry Scottish wind south across the B6 boundary between Scotland and England, the system operator pays wind farms to turn down and other plants to turn up, so the system stays stable. The constraint bill rises in windy, low-demand months. It is the British equivalent of Germany's redispatch, with a published price.
A constraint payment is a managed grid-stability cost: wind paid to turn down and other plants to turn up. It is a published cost that consumers ultimately pay.
Grid carbon intensity by region. Wind-rich Scotland and the nuclear and hydro north read far cleaner than the gas-heavy regions: the same north-clean, south-constrained split that drives the constraint payments above.
Mean grid carbon intensity across Britain's 14 local distribution-network regions. Source: NESO Carbon Intensity API (regional); boundaries: the licence areas of the 14 distribution network operators (DNOs).
Germany, the Nordics and Britain all face renewable-rich regions a congested grid can't fully serve. Germany keeps one price and curtails and redispatches; the Nordics split into price zones; Britain pays constraints. Each has trade-offs; Wattlas shows the mechanism and leaves the verdict to you.
Questions
What do grid bottlenecks cost Britain?
About £7.6 billion over the 55 months from April 2022 to October 2026, roughly £1.7 billion a year, by the count of NESO, Britain's grid operator. That is the cost of thermal constraints: paying generators, mostly Scottish wind, to switch off when lines would overheat carrying their power south.
What was the costliest month for Britain's grid bottlenecks?
September 2026, at about £474 million, by the count of NESO, Britain's grid operator, over the 55 months from April 2022 to October 2026. Britain keeps one national electricity price, so the cost of moving power south shows up in these payments to generators.
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