How we calculate wind capture rates
This page explains how the monthly wind revenues report measures what utility-scale wind earned in the NEM: the capture price, the capture rate, and the steps between the average price and the price wind captured.
Key definitions
Capture price
The capture price is merchant spot revenue, after marginal loss factors (MLFs), per MWh of available generation.
Available generation is AEMO's unconstrained intermittent generation forecast (UIGF), or the availability the farm offered where that is higher, in each 5-minute interval. The UIGF is what the wind would have let a farm generate, before outages, constraints or bidding. Dividing by available generation rather than dispatched output means curtailed and unavailable energy counts against the capture price. A farm that is constrained off at high prices shows it in its capture price.
Average RRP
The average regional reference price (RRP) is the simple average of every 5-minute price in the month, around the clock, negative prices included. For the NEM, it is the average of the five regional averages, weighted by each region's wind UIGF.
Capture rate
A capture rate above 100% means wind earned more per MWh than the average price, which happens when it generates into higher-priced periods.
Excluding negative prices
The report also quotes the capture price with dispatched output valued at zero, rather than below it, whenever the price was negative. The gap is what the fleet gave up by generating through negative prices. Many wind farms do this deliberately, because a PPA or LGC contract pays them per MWh regardless of the spot price.
The capture-price bridge
The bridge explains the gap between the average RRP and the capture price in five steps. Each step is in $/MWh of available generation, and the steps add up exactly: the average RRP plus the five steps equals the capture price, with no residual.
Until the fourth step, every price is floored at zero. So the first three steps compare positive prices only, and the cost of negative prices is counted once, in negative price dispatch.
| Step | What it measures |
|---|---|
| Price shape | The price wind's available output met, with negative prices at zero, against the average RRP. It bundles two effects: timing, meaning when wind blows relative to the price profile, and cannibalisation, meaning wind's own output pulling the price down when the fleet generates together. We don't separate the two, because doing so needs a model of where prices would have cleared without that wind. Charts label this step "Price shape (timing and cannibalisation)". It is positive when wind generates into higher-priced periods. Apart from an MLF above 1, it is the only step that can add value. |
| Unavailability | Output the wind allowed but the turbines could not deliver, such as outages and maintenance: the gap between UIGF and the availability the farm offered, valued at the floored price. |
| Curtailment | Available output that was not dispatched, for any reason: network constraints or the farm's own bids. It is valued at the floored price, so curtailing into a negative price costs nothing and is not a gain. |
| Negative price dispatch | The negative prices charged on output that was dispatched while the price was below zero. Always a cost. |
| MLFs | The effect of each farm's marginal loss factor on its revenue. A cost when the MLF is below 1, a gain when it is above. |
Why floor prices at zero? If every volume were valued at its actual price, curtailing output into a negative price would show up as a gain. The floor counts negative prices only where wind actually generated through them. Avoiding a negative price is worth zero, not a credit.
Worked example: the NEM in October 2026
| Step | $/MWh | % of RRP |
|---|---|---|
| Average RRP | 73.52 | 100.0 |
| Price shape | −7.55 | −10.3 |
| Unavailability | −0.05 | −0.1 |
| Curtailment | −5.72 | −7.8 |
| Negative price dispatch | −2.23 | −3.0 |
| MLFs | −2.96 | −4.0 |
| Capture price | 55.00 | 74.8 |
The report's charts draw the bridge the same way: columns built up from $0, with the capture price at the bottom, the costs stacked above it and the average RRP as a line. When price shape is a gain, the column finishes above the RRP line, and the part above the line is what price shape added.
Network and economic curtailment
The bridge charges all curtailment as one step. The report still splits curtailed volumes in two, for the curtailment rates it quotes and the network-constraint view of the asset map:
- Network curtailment is output spilled while AEMO's local price for the unit sat below the regional price, meaning a network constraint was binding on it. This uses AEMO's local price from December 2023; before then, the split falls on the sign of the regional price.
- Economic curtailment is the rest: output the farm chose not to generate, usually because the price was below its offer.
Aggregating to states and the NEM
- Capture prices, capture rates and bridge steps are weighted by available generation: summed revenue over summed UIGF across the units. A unit that barely ran carries little weight, whatever its capacity.
- The NEM average RRP is the UIGF-weighted average of the regional RRPs, so the price wind is measured against sits in the same regions, in the same proportions, as its output.
Data and limitations
- Sources. AEMO 5-minute dispatch data for unit output, availability, UIGF and regional prices; AEMO local prices for the constraint split; AEMO published MLFs; and Modo's Global Asset Library for status, live dates and capacity.
- Completeness. A month needs at least 95% of its 5-minute intervals to be included.
- Merchant only. The figures do not include LGCs, PPAs or other contracted revenue.