Hosting capacity API
Hosting capacity, with the method behind every figure
Hosting capacity is how much new generation or demand an operator says a part of its network can take. Every operator computes it differently. This API serves each figure with the methodology that produced it, so a number is never read under the wrong one.
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The same word, computed a dozen ways
One operator subtracts reserved and pre-reserved capacity before it publishes; another publishes the total and lists the queue separately. One studies the network with an outage (N-1), another without. One publishes firm capacity, another offers more with a curtailment band. A table that puts their numbers side by side without saying so is wrong in a way that looks right.
Here each value points at a versioned methodology: its network state, what it already subtracts, whether its figures may be summed across assets, and a comparability class. Values from different classes can be fetched together, but never silently compared.
How hosting capacity is represented
- available is what remains by the operator's own method; total is the capacity before anything is subtracted. They are different measures and never merged.
- The methodology's includes_reserved, includes_allocated, includes_pre_reserved and includes_pending_requests say what the operator already took off.
- non_additive marks figures that must not be summed across assets, because they share upstream constraints.
- Flexible capacity carries its curtailment band; conditional capacity is kept apart from firm.
- Forward-looking values carry a horizon (a target year such as Y+2), and forecast pathways a scenario.
Endpoints
| Method | Path | Returns |
|---|---|---|
| GET | /v1/capacity/search | Filter by availability_type, firmness, curtailment_max_pct, horizon. |
| GET | /v1/methodologies/{id} | One methodology: basis, network state, inclusions. |
| GET | /v1/sources/{id} | A source's manifest, methodologies and rights evidence. |
| GET | /v1/substations/{id}/capacity/history | How a series changed over time (Pro). |
Example
Request
curl "https://api.gridcapacityapi.com/v1/capacity/search?direction=injection&firmness=flexible&curtailment_max_pct=10&horizon=Y%2B2&comparability=strict" \ -H "Authorization: Bearer gc_live_..."Strict mode asked for one comparability class and the filters matched two, so the API answers 422 and names the classes instead of mixing them. Add a country or source filter, or use best_effort and read the warnings.
Response shapeplaceholder values — not a capacity claim
{
"error": {
"code": "capacity_semantics_not_comparable",
"message": "The requested sources cannot be compared under strict comparability mode.",
"request_id": "req_…",
"details": {
"classes": [
"…",
"…"
]
}
}
}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.
| Country | Status | Sources served | Assets | Newest operator date |
|---|---|---|---|---|
| United Kingdom | Partial | 14 | 4,920 | 14 Aug 2026 |
| Netherlands | Partial | 3 | 1,245 | 13 Sep 2026 |
| Belgium | Live | 3 | 1,139 | 24 Sep 2026 |
| France | Live | 3 | 5,237 | 25 Aug 2026 |
| Spain | Partial | 0 | 16,467 | 9 Sep 2026 |
| Portugal | Partial | 0 | 461 | 11 Jul 2026 |
| Austria | Partial | 0 | 443 | 29 Jul 2026 |
| Denmark | Live | 1 | 160 | 1 Feb 2026 |
| Italy | Partial | 0 | 110 | 1 Sep 2026 |
| Switzerland | Live | 1 | 778 | — |
What people build with it
Firm versus flexible
Compare the capacity an operator offers firm with what it offers under a curtailment band, per technology and horizon.
Tracking headroom
Follow each series as operators republish, and see when headroom at a node opened up or disappeared.
Methodology-aware analysis
Aggregate only what may be aggregated, and compare only what shares a comparability class.
Questions
Why is there no single “available MW” field?
Do you compute hosting capacity yourselves?
What if an operator publishes a traffic light instead of a number?
Start building on grid-capacity data
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