Renewable output: bridge curtailment and captured prices
A renewable generator’s installed megawatts do not determine its realized revenue. Available wind or sunshine, outages, curtailment, the hours of production and contract settlement all matter. Connect physical output to the price actually captured before using average wholesale prices to explain the operator’s economics.
Separate capacity, potential output and delivered energy
The EIA defines capacity factor as actual electrical energy divided by the energy possible at continuous full-power operation over the same period. The denominator requires a compatible capacity rating and time window. It does not identify why generation fell below that maximum.
The EIA’s discussion of California curtailment explains how congestion and oversupply can reduce renewable output through price signals or dispatch instructions. This is a specific market example, not a universal contract rule or a claim about every generator’s compensation.
Assume a hypothetical 100 MW facility operates over 1,000 hours. Full-power energy is 100,000 MWh. Resource conditions could have produced 40,000 MWh, but 5,000 MWh are curtailed. Delivered generation is 35,000 MWh and actual capacity factor is 35%, rather than the 40% resource-potential ratio.
A hypothetical captured-price calculation
Assume the observation period has two equally long price blocks, with prices of 20 and 60 per MWh. The facility delivers 20,000 MWh in the lower-price block and 15,000 in the higher-price block.
| Hypothetical block | Delivered MWh | Price | Energy revenue |
|---|---|---|---|
| Lower-price block | 20,000 | 20 | 400,000 |
| Higher-price block | 15,000 | 60 | 900,000 |
| Total | 35,000 | Output weighted | 1,300,000 |
The equal-hour average market price is 40, but captured price is 1,300,000 / 35,000, approximately 37.14. A generator producing more during lower-price hours earns less than the simple market average. Multiplying actual output by 40 would overstate energy revenue by 100,000 in this example.
Add the contract settlement explicitly
Now assume a separate hypothetical financial contract settles 25,000 MWh at a fixed price of 50 against an agreed reference index of 40. Settlement received is 250,000. Together with spot revenue, total receipts are 1.55 million, approximately 44.29 per delivered MWh before other costs.
This example assumes the contract quantity and reference index exactly as stated. A pay-as-produced arrangement, hourly shape obligation, nodal basis or negative-price clause can produce a different result. Do not treat a contract’s fixed price as the realized price on every generated MWh unless the terms justify that assumption.
Observe the constraint and the compensation
Record potential generation, outages, curtailment, delivered output, hourly market values and contract settlements separately. Lost physical output may or may not receive compensation. A compensated curtailment payment does not restore energy delivered, and an uncompensated curtailment event cannot be valued at a positive average price without checking the affected hours.
Review when output increases but captured price falls, when congestion shifts to the facility’s connection point, or when a contract approaches expiry. These trigger checks of production shape, location basis and future commercial exposure. They do not automatically imply mechanical underperformance.
The final worksheet explains the generator’s physical-to-cash chain under defined market and contract conditions. It excludes debt service, taxes, operating costs and any separately sold environmental attributes. It therefore cannot be read as net profit, a price forecast or evidence that installed capacity earns a guaranteed return.
A portfolio average can also conceal very different connection points. Two projects with similar resource quality may capture different prices because one faces local congestion. Keep each project’s delivered energy and settlement location intact before aggregating receipts. If only regional prices are public, label the comparison as a regional proxy and show the missing node-level basis. An apparently precise captured-price estimate is not improved by substituting an unrelated market hub without disclosure.
FAQ
Does a lower capacity factor prove the equipment failed?
No. Resource conditions, curtailment and outages can all reduce it. Inspect the separate energy-loss categories before assigning a cause.
Does a fixed-price contract eliminate every price exposure?
No. Quantity, timing, location, settlement index and exclusions can leave differences between the contract and actual production. Read the relevant agreement.