Scotland’s Biggest Offshore Wind Farm Wasting Three Quarters of Energy

I think you’re mistaken. This is what ChatGPT says:

**Short answer:**
Yes — in the UK market, *any situation in which the system operator (currently the National Energy System Operator, NESO) takes action to reduce or curtail a wind farm’s output because that power cannot be safely absorbed by the grid will generally give rise to a **constraint payment** (a curtailment payment). That includes when high wind production coincides with low demand *and* the grid cannot use or export all that power. ([renewableuk.com][1])

### 🟡 **What “constraint payments” are**

* **Constraint payments** are compensatory payments made via the Balancing Mechanism when a generator is instructed to *reduce* output for system-balancing reasons (e.g., transmission constraints or excess supply). ([renewableuk.com][1])
* They’re designed to compensate generators for lost revenue and any forfeited subsidies when they can’t generate the electricity they *would otherwise* have sold or been paid for. ([ref.org.uk][2])

### 📊 **When constraint payments are triggered**

Constraint payments typically arise when the system operator needs to *curtail* generation to keep the grid stable. There are two broad reasons that can lead to curtailment actions where constraint payments arise:

#### **1. Physical grid capacity constraints**

This is the classic case:
If *transmission capacity* is limited — for example, high wind generation in Scotland but not enough capacity on cables to carry that power south — then NESO will ask wind farms to reduce output. Constraint payments are made because their power *cannot physically be transmitted to demand centres*. ([renewableuk.com][1])

#### **2. Supply exceeding demand and grid limits**

Even if there *is* transmission capacity available in theory, the system still needs to balance **supply and demand** in real time.
Electricity can’t be stored easily in large volumes; the grid needs instantaneous balance. If there’s *too much supply* relative to demand and system conditions (voltages, frequency) would be threatened, the system operator may also curtail generation.

In practice, high wind + low demand days (e.g., windy weekends or overnight) can create this situation. On such occasions, wind farms are often paid to stop generating because the grid cannot accept all their power **even though the bottleneck may be a system balancing constraint rather than strictly a transmission capacity limit**. ([National Energy System Operator (NESO)][3])

👉 In other words: **constraint payments are triggered by actions to reduce output needed to protect the grid — whether due to transmission bottlenecks *or* because overall generation exceeds demand in the moment.** Both are part of the wider “Balancing Mechanism.” ([ref.org.uk][2])

### 🧠 **Why this happens in practice**

Because wind is variable and often concentrated in areas distant from large demand centres (e.g., offshore or northern onshore), the system sometimes ends up with:

* **Excess instantaneous supply** — e.g., very windy with low usage (overnight/weekends), or
* **Grid transmission constraints** — e.g., lines at thermal limits between regions.

In either case, the operator may *curtail* wind generation and compensate the generator under balancing/constraint arrangements. ([renewableuk.com][1])

### 📌 **Clarifying a common confusion**

It’s *not only* the narrow technical transmission “grid capacity” constraint that leads to payments:

* If wind output is so high that **total supply would dangerously exceed demand** or create imbalance issues even with available transmission capacity, the operator still curtails generation and pays for it.
* In operational terms, all such actions occur in the *Balancing Mechanism*, and payments made for reducing generation are classed as constraint/curtailment payments. ([ref.org.uk][2])

### 📉 **Related impacts**

* These payments are ultimately recovered through charges on consumer bills. ([renewableuk.com][1])
* They’re expected to rise as renewables grow faster than grid upgrades. ([Power Technology][4])

**Bottom line:**
So, *yes* — if a wind farm is generating power that *cannot be used by the grid at that moment*, whether because of peak wind/low demand or because of physical network limits, and the system operator instructs it to curtail output, that generally *does* lead to a constraint/curtailment payment under current UK balancing arrangements. ([renewableuk.com][1])