Generation Curtailment

Overview

This page shows curtailment energy recorded by the electricity system operator's Balancing Mechanism, for the twelve months from 04 Aug 2025 to 14 Jul 2026, normalised against each area's total connected generation and storage capacity so that curtailment can be compared fairly between larger and smaller areas. The map shows a rate per unit of capacity (megawatt-hours curtailed per megawatt connected) — not how many hours an area was curtailed, but how intensively its capacity was curtailed.

These two views below do not reconcile with one another. Each matches generating units to a geography — GSP area or SSEP zone — using an independent method, and each has its own coverage gap: 83.5% of units (551 of 660) resolve to an SSEP zone, and 72.7% (480 of 660) resolve to a GSP area. Every GSP-area-matched unit is also SSEP-zone-matched, so the SSEP zone view below covers more units overall. Treat each view as internally consistent on its own terms, but not comparable row-for-row against the other.

Unmatched (no resolved zone), excluded from the SSEP zone map above: 849.32 MWh for this technology.

Data sources

• Curtailment volumes: the electricity system operator's Balancing Mechanism instruction records, filtered to system-operator-directed reductions in output — this isolates genuine curtailment from routine commercial dispatch.
• Connected capacity (the denominator): NESO's Transmission Entry Capacity (TEC) register, which records the agreed connection capacity for each generation and storage project. This denominator is technology-blind: it's the total connected capacity of every technology in the area/zone, not just the curtailed technology's own capacity — deliberately, because roughly 9% of connected capacity sits on projects registered against more than one technology with no published per-technology split. The trade-off: an area with a small, heavily curtailed technology (e.g. wind) alongside a large, rarely curtailed one (e.g. gas) can show an artificially low normalised figure for the curtailed technology.
• Matching generating units to a geography: neither register publishes a generating unit's coordinates directly. We match each unit against several independent datasets — open mapping data, distribution network records, and manual review for low-confidence candidates — to resolve a location, then match that location to the GSP area or SSEP zone containing it. Coverage differs between the two views: 83.5% of units (551 of 660) resolve to an SSEP zone, versus 72.7% (480 of 660) to a GSP area — every GSP-matched unit is also SSEP-zone-matched. The SSEP zone view surfaces its unmatched units' total curtailment separately (see "Unmatched" below the map); the GSP area view has no equivalent — unmatched units are simply excluded from every GSP figure with no visible total.
• Offshore SSEP zones are excluded from the zone map: we only ever resolve connected capacity (the denominator) for onshore zones, so the normalised metric plotted on the map can never be computed for offshore zones — this is a structural gap, not missing data. Offshore zones can still record genuine curtailment (well under 1% of the total across all zones in the current window).