NEM Market Structure and FCAS
NEM market structure and FCAS concentration
Market power is a precondition for most of the conduct on the conduct monitor page. These panels show where it exists: which parent groups the market could not do without at the evening peak, how concentrated available capacity is in each region, and how few groups earn each FCAS service's revenue.
Pivotal means regional demand could not be met by every other group's available capacity plus interconnector imports: Residual Supply Index = (regional available capacity + import capability - group's available capacity) / operational demand, below 1. The sample is the 17:00, 18:00 and 19:00 dispatch intervals (NEM time) of every day in the last 12 months.
HHI (Herfindahl-Hirschman Index) is the sum of squared percentage shares: 10,000 when one group holds everything, above 2,500 conventionally treated as highly concentrated.
Share of evening-peak intervals each group was pivotal (RSI below 1)
Concentration of available capacity at the evening peak (HHI)
Largest group's share of available capacity by region and month
FCAS revenue concentration by service, NEM-wide (HHI)
FCAS concentration by region and service, last 60 days
Unit-hours of floor-priced offers behind binding constraints
Method and caveats
- Available capacity is DISPATCHLOAD availability: offered MAXAVAIL for scheduled units, UIGF for semi-scheduled wind and solar. Withheld capacity therefore lowers a group's measured share. Scheduled loads are excluded.
- Each DUID is assigned to the participant that bid it in the last 30 days, then to a parent group. Units that changed hands earlier in the window are shown under the current bidder, and retired units fall into "Other".
- FCAS concentration is measured on revenue (enabled MW times the regional FCAS price, from the pre-aggregated daily DUID revenue table), because unit-level enablement over 18 months exceeds what a dashboard query may read. Revenue share weights high-price intervals more heavily than enablement share would. The regional table attributes revenue to the unit's region.
- Race-to-the-floor exposure counts unit-hours in which a unit whose first price band that day was at or below -$900/MWh had a local price below the regional price because of a binding constraint. Most wind and solar offer at the floor as a matter of course, so this measures where floor bidding meets network congestion, not intent.