Description:
Scottish wind farms generate nearly half of Great Britain's wind power, but in 2025, turbines there were paid £350 million to switch off. At the same time, Britain spent over a billion pounds firing up gas to replace it. The total bill: £1.35 billion. And it's passed directly onto consumers in their energy bills.

So why is wind curtailment in Great Britain happening, and why is it getting worse?

This is the story of grid constraints. What they are, why they happen, and why solving them is one of the most urgent challenges on the path to clean power. In this documentary, we examine the infrastructure and market constraints behind Great Britain's wind curtailment problem: the transmission bottlenecks between Scotland and England that cap how much clean power can flow south; the B4 and B6 grid boundaries where constraints are most severe; the role of the National Energy System Operator (NESO) in managing the grid in real time; and why gas still dominates over batteries when constraints hit.

We also look at the three routes available to fix the problem and why none of them are straightforward.

This is why Great Britain pays to turn off the wind - and what it would actually take to stop.

Our guides are Robyn Lucas, Head of GB at Modo Energy, and Ed Porter, Director EMEA & APAC at Modo Energy. Together they break down:

• Why Scotland generates nearly half of GB's wind power - but can't send it south
• What happens inside the NESO control room when a constraint hits
• Why the curtailment bill has grown from a few hundred million in 2018 to £2.7 billion today
• Why batteries haven't replaced gas - yet
• What transmission investment, storage, and market reform could each deliver

Chapters:
0:00 Why Britain pays to switch off the wind
0:54 Scotland's wind problem explained
1:36 What is a grid constraint?
1:57 The B4 and B6 boundaries
2:44 Inside the NESO control room
3:21 Why gas fills the gap and where batteries fit
4:35 The two-part cost of curtailment
5:17 How volatile gas prices make it worse
6:10 Is 30–40% curtailment normal?
6:30 Fix 1: Build more transmission
7:10 Fix 2: More storage and flexibility
7:47 Fix 3: Market reform
8:35 Closing

Music licensed via Artlist.

Stock footage licensed via Pond5 (via Everly).

This video is for informational purposes only and does not constitute investment advice.

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​Transcript:
If you’re seeing wind farms being turned down and gas being turned up, I think there is a natural instinct to say, well, hold on, what’s actually happening here? That’s costing us 1.4 billion pounds a year. But the problem is not the wind generation. It’s that we don’t have the network to take the wind generation to where it’s needed — the demand in the South.
In 2025, Scottish wind farms were paid 350 million pounds to turn off. At the same time, Britain paid over a billion pounds to fire up replacement power elsewhere, mostly gas. The overall bill came to 1.35 billion pounds.
This bill is passed on to consumers. The reality is that maybe those wind turbines are doing exactly what they’re supposed to be doing — which is being turned down because there’s too much wind generation on the system. So how did we get here? Let’s start with the generation.
Scotland is one of the windiest places in Europe. Almost 15 gigawatts of wind capacity has been built there. That’s roughly half of Britain’s entire wind fleet. Wind farms in Scotland generate electricity, which is transported south to areas of high demand — cities like London, Birmingham, and Manchester — through transmission lines.
The transmission lines connecting Scotland to the rest of Great Britain can carry around six gigawatts at any time. On a windy day, Scottish wind farms can produce ten. Four gigawatts of clean electricity with nowhere to go. The grid experiences something called a constraint.
A constraint is when you’re trying to flow more power through a transmission line than it can actually carry. If you ran too much power for too long, you would break that transmission line. Now, in order to manage these constraints, the electricity generators — in this case, wind farms in Scotland — need to be curtailed. In other words, turned off.
The grid is divided by transmission boundaries — invisible lines on the map marking where the wires become a bottleneck. The main one between Scotland and England is called the B6, but the worst constraint right now is further north, inside Scotland itself. We see the most amount of constraints in Scotland, and particularly in North Scotland. The boundary called B4, which is in the north of Scotland, has got a load of onshore wind sitting behind it and some offshore wind connecting in, and that is where we see the most constraints happening on the system.
When more wind tries to flow through those boundaries than the wires can carry, someone has to intervene. One organisation solves these constraints in real time. The National Energy System Operator — NESO — is responsible for keeping the lights on across Great Britain, every second of every day. When a constraint hits, the system operator in the control room will see that we have too much generation in one place.
And so if that’s in, say, Scotland — let’s say we’ve got three gigawatts generating, but we’ve only got capacity to get two gigawatts down to below the constraint — then they’ll need to turn down those generators in Scotland by one gigawatt, and they’ll need to find one gigawatt of replacement power from below that constraint. So the wind farm gets an alert — turn it down. Now there’s a gap to fill. Historically, most of that replacement generation has been provided by gas plants, which are flexible and can run for as long as a constraint lasts — often eight to twelve hours, and sometimes even days.
What is now competing with gas is batteries. You can use them to offset some of that power that has been turned down, but they have a limited duration. You might get two hours’ worth of power from a battery, whereas a gas plant can go on for a lot longer. What batteries can do that gas cannot is help on both sides of the constraint — storing surplus power behind it, and discharging in front of it to replace what was lost.
Historically, gas has dominated. Batteries are cheaper, but their shorter duration and limitations in how NESO dispatches them means they aren’t used to their full capability. When we get those constraints, it’s easy to think that someone’s doing something wrong — that the wind farm shouldn’t be being turned down, or the gas shouldn’t be being turned up. And the reality is that each of those elements is doing the thing that they’re being instructed to by the system operator.
When we get really high constraint costs coming through, it’s more of a system design issue, or it’s things like a lack of transmission capacity. Every time wind is curtailed, there’s a two-part bill.
Part one: the wind farm is compensated for the power it didn’t get to sell. This is not a bonus. It’s compensation. Most modern wind farms operate under an agreement called a Contract for Difference, which guarantees them a fixed price for every unit of energy that they generate.
When they’re told to stop generating, they’ll charge the system operator to make up for that lost revenue from the energy they would have produced. When those assets are then turned down, they get compensated back up to that level, because the curtailment happening is something that is deemed to be outside of their control. That’s the smaller part of the bill. The second part is what gets paid for the replacement power that gets turned on instead, and that cost moves with the global gas market.
When we rely on gas to manage constraints, we are essentially asking those gas units to turn on, which comes at a price, and that price is dependent on the gas price and the carbon price. Now, those gas prices can be very volatile. And so if we have things like a war in the Middle East, that will bring up gas prices globally, and that will mean that our balancing costs will be higher. The cost of managing these constraints has ballooned.
This represents a huge risk to us getting to net zero. The public perception of renewables is going to be that they’re really expensive, because that’s all that people are seeing — turning down wind is costing us a fortune. We’re generating all this clean power, building all this infrastructure, but we’re turning it down. What’s the point?
Research suggests that an efficient grid can expect about 5% of its renewable output to be curtailed. So the problem now is significant. We are turning down 30 to 40% of the wind that is produced in Scotland. We are currently facing significant constraints in Scotland that really make the system more inefficient.
So how can we reduce wind curtailment and make the grid more efficient? Britain has three routes available.
The first: build more transmission — more wires, more capacity. But new lines can take up to ten years to build, and you have to be strategic. If we fix the B4 — which means build more wires in northern Scotland — we’d resolve those constraints. But we would then have more constraints at the next boundary south, which is at the B6.
It’s a little bit like opening locks in a canal. The water flows into the next section, but then it gets stopped by the next lock. So we would actually need to build more wires in the south of Scotland as well.
The second: develop more storage and flexibility. Building and utilising batteries either side of the constraint can reduce the cost of curtailment and avoid wasting cheap clean energy. Batteries charge during periods of surplus wind and discharge when the grid needs power. Placed on both sides of the constraint, they can manage the flow across the boundary, reducing curtailment without the need to build major transmission infrastructure.
Long-duration storage and demand flexibility can provide this as well.
The third: reform or redesign the market. Right now, generators across Great Britain respond to a single national price signal — one that doesn’t reflect where power is actually needed, or where there’s already too much. A locational approach would give generators a real signal about where to build and when to generate. This kind of locational pricing isn’t untested — grids in Texas, California, and many others in the United States already operate this way.
The British government considered a full redesign, but instead opted to reform the current market. The idea is that the changes in that reformed national price will give us a system that works better locationally. We are yet to see what that really looks like. And it may be the case that if reformed national pricing doesn’t do the job it’s supposed to, we might go back to a system like zonal.
The wind resource is there. The technology works. But we’re building the energy system of the future on a grid built for the past. Scotland’s wind isn’t the problem.
It’s the answer. Britain just hasn’t built the infrastructure to take advantage of it yet.