UK grid capacity API

The GB capacity heatmaps, in one schema

Ofgem's Long Term Development Statement requires every GB distribution network operator to publish a capacity heatmap in one standard JSON format. The API reads each operator's file where it is openly available and serves it with the operator's own licence terms.

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One standard, six operators, fourteen licence areas

The Form of LTDS asks for capacity heatmaps refreshed on or before 31 May and 30 November each year, in a JSON information model. In practice each operator ships it differently: as portal attachments, alternative exports, keyed datasets, or behind a bot challenge. Field spellings drift, and headroom arrives in MVA, alongside a red-amber-green status and a limiting factor.

The API keeps the MVA as MVA. Converting it to MW would need a power factor the operators do not publish, so value_mw is null and an MW filter will not match these records; filter with unit=MVA instead. The RAG status and the limiting factor travel with the value.

What the heatmaps publish

Per substation: demand headroom, generation headroom and reverse-power-flow capacity, in MVA.
A red-amber-green status and the constraint that limits headroom, carried verbatim in the record's details.
A twice-yearly refresh cycle, with each file's own date as the operator's effective date.
Licences that are mostly open (CC BY 4.0, or the operator's own open-data licence permitting commercial use), shown per source with the attribution each asks for.

Endpoints

Method	Path	Returns
GET	/v1/capacity/search?country=GB&unit=MVA	Every heatmap record in MVA, filterable by direction.
GET	/v1/operators?country=GB	The GB operators and their sources.
GET	/v1/sources/{id}	One operator's heatmap: licence, cadence, health.
GET	/v1/capacity/nearby	Headroom around a site, nearest first.

Example

Request

$ curl "https://api.gridcapacityapi.com/v1/capacity/search?country=GB&direction=injection&unit=MVA&min_capacity=10" \  -H "Authorization: Bearer gc_live_..."

min_capacity filters in the requested unit. min_capacity_mw would return nothing here, by design: none of these values is in MW.

Response shapeplaceholder values — not a capacity claim

{
  "data": [
    {
      "id": "cap_…",
      "series_id": "cs_…",
      "asset": {
        "id": "sub_…",
        "type": "substation",
        "name": "…",
        "slug": "…",
        "country": "GB",
        "operator": {
          "id": "op_…",
          "slug": "…",
          "name": "…",
          "type": "DSO"
        },
        "network_level": "…",
        "voltage_kv": 33,
        "location": {
          "type": "Point",
          "coordinates": [
            0,
            0
          ],
          "precision": "exact"
        }
      },
      "direction": "injection",
      "technology": "generic_generation",
      "capacity": {
        "type": "available",
        "value": 0,
        "unit": "MVA",
        "value_mw": null,
        "qualifier": null,
        "status": null,
        "status_label": null
      },
      "firmness": "firm",
      "curtailment": null,
      "horizon": {
        "type": "snapshot",
        "year": null,
        "label": null
      },
      "methodology": {
        "id": "…",
        "comparability_class": "…",
        "non_additive": true,
        "binding": false
      },
      "freshness": {
        "source_effective_at": "…",
        "retrieved_at": "…",
        "last_confirmed_at": "…",
        "source_health": "healthy"
      },
      "provenance": {
        "source_id": "…",
        "source_url": "https://…",
        "license": "…",
        "rights_mode": "…"
      },
      "access": {
        "status": "granted",
        "attribution": "…"
      },
      "decision_context": {
        "binding": false,
        "formal_connection_study_required": true,
        "source_indicative": true,
        "statement": "The operator's latest published dataset reports … under methodology …."
      },
      "details": {
        "limiting_factor": "…"
      }
    }
  ],
  "pagination": {
    "has_more": true,
    "next_cursor": "…",
    "limit": 20
  },
  "meta": {
    "request_id": "req_…"
  }
}

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What the API holds today

Read from the API as this page renders. A source is listed with its rights status, because a listed source is not always a served one.

Sources the API holds for GB
Source	Operator	Rights	Health	Cadence	Last success
ENWL Heatmap Tool	SP Electricity North West	Archived, pending review	Healthy	When the operator updates it	5 h ago
ENWL capacity heatmaps	SP Electricity North West	Archived, pending review	Disabled	Monthly	never
NESO connection registers (TEC, Embedded, Interconnector)	National Energy System Operator	Granted	Disabled	Unknown	never
NGED LTDS Capacity Heatmap	National Grid Electricity Distribution	Granted	Disabled	Twice a year	never
NGED Network Capacity Map data	National Grid Electricity Distribution	Archived, pending review	Disabled	Unknown	never
NIE Networks Capacity Map	NIE Networks	Registry only	Disabled	When the operator updates it	never
NPg GSP connection information	Northern Powergrid	Granted	Healthy	When the operator updates it	5 h ago
Northern Powergrid Heat Map Data	Northern Powergrid	Granted	Healthy	Monthly	5 h ago
Northern Powergrid LTDS Capacity Heatmap	Northern Powergrid	Granted	Disabled	Twice a year	never
NPg Network Development Plan headroom	Northern Powergrid	Granted	Healthy	Yearly	5 h ago
SP Energy Networks Capacity Heatmap — SPD	SP Energy Networks	Granted	Healthy	Twice a year	5 h ago
SP Energy Networks Capacity Heatmap — SPM	SP Energy Networks	Granted	Healthy	Twice a year	5 h ago
SPEN Network Scenario Headroom Report	SP Energy Networks	Granted	Disabled	Yearly	never
SSEN GSP Technical Limits	SSEN Distribution	Granted	Healthy	When the operator updates it	5 h ago
SSEN Headroom Dashboard	SSEN Distribution	Granted	Healthy	When the operator updates it	5 h ago
SSEN Distribution LTDS Capacity Heatmap	SSEN Distribution	Granted	Healthy	Twice a year	5 h ago
UKPN DFES Network Scenario Headroom Report	UK Power Networks	Granted	Disabled	Yearly	never
UK Power Networks LTDS Capacity Heatmap	UK Power Networks	Granted	Healthy	Twice a year	5 h ago

What people build with it

GB site finding

Screen every GB licence area for generation or demand headroom with one query and one schema.

Twice-yearly diffs

See which substations gained or lost headroom when a new heatmap lands, from the change feed.

Portfolio monitoring

Watch the substations behind a project pipeline and get a webhook when their figures move.

Questions

Why MVA and not MW?

Because the heatmap standard publishes apparent power. Turning it into active power needs a power factor for each site, which the operators do not publish, and inventing one would be a figure nobody published.

Are all six operators included?

The table on this page is read from the API and lists exactly what it holds, with each source's rights status and health. Some operators serve the standard file only to registered users or behind a bot challenge, and those are used only with the operator's own access arrangements.

Is the heatmap a connection offer?

No. The operators describe the heatmaps as indicative; a connection needs an application and a study.

Units and MVA Rights and attribution United Kingdom coverage

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