Methodology & caveats

• Market signal, not metered flow. Congestion is inferred from IEX day-ahead bid-area price separation. POSOCO does not publish per-corridor MW, so we never claim a causal corridor flow — this is a price discriminator.
• Regions from areas. IEX areas group by first letter: N→Northern, W→Western, S→Southern, E→Eastern, A→North-Eastern. Each region’s price is the mean of its areas; the national reference is the cross-region median (robust to a single capped area).
• Stress index. A 0-100 blend of market exposure (45%), interchange deviation (35%) and curtailment (20%), renormalized over whichever components have data, with per-state confidence.
• Curtailment coverage is report-driven. Compiled from Grid-India NLDC/REMC daily + Rajasthan SLDC + SRLDC reports. Absence of a row is not proof of zero curtailment.
• Interchange stress uses scheduled-vs-actual state drawal; the state board snaps to the latest day with broad (≥20-state) coverage.

Congestion is inferred from IEX bid-area price separation — a market signal, not a metered corridor flow (POSOCO does not publish per-corridor MW). Curtailment is compiled from Grid-India NLDC/REMC + SLDC reports.

Frequently asked

What is grid congestion in India's power market?

Grid congestion happens when a transmission corridor can't carry all the power the market wants to move across it. On the IEX day-ahead market it shows up as price separation: when two bid areas clear at different prices in a 15-minute block, the corridor between them is binding. India mostly clears at a single national price, so congestion is episodic rather than constant.

How is congestion measured here?

From IEX bid-area clearing prices. India's areas group into five regional grids (N→Northern, W→Western, S→Southern, E→Eastern, A→North-Eastern). For each 15-minute block we compare each region's price to the cross-region median; a corridor is 'binding' when the two regions differ by more than ₹100/MWh. This is a market signal, not a metered corridor flow — POSOCO does not publish per-corridor MW, so we never claim a causal flow.

What is the congestion stress index?

A transparent 0-100 per-state score that blends three signals: market price-separation exposure (how far the state's region priced away from national), physical interchange deviation (how far actual inter-state drawal drifted from schedule), and reported renewable curtailment. Only components with data contribute — their weights are renormalized over what's present, and every state carries a coverage and confidence breakdown.

What is renewable curtailment and where does it happen?

Curtailment is renewable generation the grid asks to switch off — usually because a transmission corridor is overloaded or the local grid can't absorb the midday solar. In India it concentrates in high-RE states: Rajasthan leads (Bhadla-area 765kV export constraints), followed by Gujarat, and with recorded events in Maharashtra, Andhra Pradesh, Tamil Nadu and Uttar Pradesh. The data here is compiled from Grid-India NLDC/REMC and SLDC reports.

Which corridor is most often congested?

Historically the Northern–Western (NR-WR) corridor is the most frequent binding constraint, with the Northern region typically the import-constrained (premium) side during high-demand episodes. The Northern–Southern link also binds when southern surplus can't reach the north.

Where can I get the data?

The national, corridor, state and curtailment series are available via the India Energy Atlas API at /api/v1/congestion/* and update daily. The page and API are open for reference use.