Open dataset
Across the seven US ISOs (2018-2025), the 1% of hours with the largest price deviation from the annual median hold a median 16% of the year's total arbitrage value, and the top 5% hold a median 37%. The most concentrated market, ERCOT, reaches 55% in its top 5% of hours.
How concentrated wholesale value is in a small number of hours, measured as each hour's price deviation from the annual median (the arbitrage a flexible load can capture by shifting out of high-price hours or into low-price ones), by ISO and year, day-ahead and real-time. The core evidence for why shifting load in a handful of hours is worth so much.
Cumulative share of annual energy value vs share of hours, by ISO and year (day-ahead market).
The same value-concentration curves computed on real-time market prices.
Median, mean, max, min, and standard deviation of LMP by ISO and year.
When the highest-value hours occur, by hour-of-day, month, and day-of-week.
How forecastable the top-value hours are, measured as recall of the next year's top-N hours.
Free to use with attribution (CC BY 4.0). These are the derived summary tables, reproducible from the primary sources.
Built from hourly day-ahead and real-time prices across each ISO. Each hour's value is the absolute deviation of its price from that ISO-year's median, |LMP minus median|: the arbitrage a flexible load captures by shifting out of high-price hours or into low-price ones. Hours are ranked by this value and accumulated to trace what share of the year's total deviation sits in the top share of hours.
Used in Markets: critical-hours value concentration.
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Cite this dataset
Corey Balgeman, "Critical-Hours Value Concentration Across US ISOs," Grid Flexibility, 2026. https://gridflexibility.fyi/data/critical-hours-value-concentration
Part of the Grid Flexibility open datasets. Provenance and methodology are published; another researcher can reproduce these tables from the primary sources. Canonical home: https://gridflexibility.fyi/data/critical-hours-value-concentration.