Congestion Calculator — methodology

1. Dispatch reconstruction — the marginal-cost merit order is walked up to the metered national residual load to estimate which units run each 15 minutes.
2. Injection — generation and load are allocated to the network by postcode-consumption weights, giving a net injection at each substation.
3. DC power-flow — a power-flow solve yields per-line flows; each substation’s loading is the worst flow-to-rating ratio across its incident lines and transformers. ≥ 100% = a binding constraint.
4. Area rollup — substations are mapped to areas via the postcode-to-substation lookup, and per-substation stress is aggregated into the worst and median loading%, plus counts over the 85% and 100% thresholds.

Three grains are exposed: PC4 (postcode block — what a developer types), grid area (the capaciteitskaart unit, the natural calibration grain), and province (the coarse rollup). Each resolves to the high-voltage substation(s) feeding it.

• Stressed — a substation at ≥ 85% loading (approaching its limit).
• Binding — a substation at ≥ 100% (a line at or over its thermal rating).
• An area is flagged congested when its worst substation is binding.

Classification-grade, not metering-grade: roughly 75–85% right on “is this area stressed?”, with ±20–30% on the absolute loading%. Suitable for screening, scorecarding, research and journalism — not real-time operations, N-1 contingency, or bankable guarantees.

Three caveats inherited by every number:

• One bidding zone. The Netherlands is a single price zone, so wholesale/imbalance prices carry no locational signal. This congestion is inferred from a physics model on metered load + the merit order — not from prices.
• Line ratings. Loadings use class-level thermal ratings per voltage tier, not per-asset nameplate values, so the absolute percentage carries error. Per-circuit ratings are a planned follow-up.
• Upstream high-voltage ceiling. The model stops at the high-voltage grid feeding each area. Most medium- and low-voltage feeder congestion a connection queue hits sits below this layer and is not captured dynamically.