Unlocking insights across MISO, SPP, PJM, and ERCOT

Picture two wind projects located in the central wind belt of the United States - built around the same period, with both experiencing similar market conditions in the form of negative nodal prices and hub-to-node price basis. Yet, one project curtails 2.5% of the time, while the other curtails its generation 14% of the time - nearly six times more often. The difference isn’t due to location, transmission congestion, or weather conditions. It comes down to the specific terms in the projects’ offtake contracts.

This is one of the many unique insights we’re uncovering through the newly expanded Curtailment Lens dashboard, available to CleanSight Reports subscribers. Previously limited to the ERCOT market, the Curtailment Lens now provides curtailment trends and project-level insights across ERCOT, MISO, PJM, and SPP, bringing the total dataset to over 500 projects¹.

Curtailment has major implications for clean energy buyers and investors, as the reduction in delivered megawatt-hours and RECs can put their sustainability targets at risk.

If your curtailment model uses regional baselines or doesn’t take offtake terms into account, you aren’t getting the full picture of your curtailment risk. In our Curtailment Lens dashboard, we use project-level data to identify periods of curtailment and provide insights on how real projects are responding to market conditions.

In the remainder of this blog post, we use data from Curtailment Lens to delve deeper into both regional curtailment trends and the impact of contract terms and tax credits at the individual project level - showing how a single contract term can create a 6x increase in curtailment.

Regional curtailment trends

Although curtailment behavior is largely project-specific, regional trends can provide a useful baseline for understanding the macro drivers of curtailment. In particular, resource concentration has a large impact on curtailment; as more wind or solar generation gets built in a particular region, oversupply conditions become more common, leading to an increase in curtailment frequency. 

As shown in the figure below, SPP has the highest amount of wind curtailment, largely driven by high wind penetration, localized transmission bottlenecks, and a limited number of high load zones. While wind curtailment frequency has steadily increased in SPP over the last ten years, with a current fleetwide average around 8%, wind curtailment frequency in both MISO and ERCOT has leveled out around 3-4% over the past few years. This is partially due to transmission upgrades in both ERCOT² and MISO³ that served to alleviate localized areas of congestion, in addition to rapid load growth in ERCOT.  As SPP makes its own needed transmission upgrades⁴ over the coming years and continues its expansion into the Western Interconnection⁵, it’s likely that wind curtailment frequency will begin to level out or even decrease in SPP.

On the solar side, ERCOT has experienced a steady increase in solar curtailment over the last two years as a result of rapid solar build-out, while solar curtailment in MISO and PJM remains low due to the relatively small solar penetration in those markets. 

Project-level dynamics: The 6x gap, explained

Although regional trends hold true on average, they mask significant variations in individual project performance. In reality, project curtailment behavior is heavily dictated by both tax credit availability and PPA contract terms. To demonstrate the impact of these factors, the figure below shows the median ratio of observed to modeled generation for three wind projects as nodal prices go negative, with ratios significantly below 1 indicating that curtailment is likely occurring. 

Nobles 2 Wind, a MISO project with a utility PPA⁶ and one of the projects from our earlier example, continues operating near its modeled potential even as prices dip into deeply negative territory. Caddo Wind, an SPP project with a corporate vPPA⁷, experiences similar market conditions to Nobles 2 but begins curtailing as soon as prices drop below -$32/MWh, the current value of the Production Tax Credit (PTC)⁸. This difference in price response leads to the 6x difference in curtailment frequency between the two projects. 

Why the drastically different response of the two projects to similar market conditions? The project behavior largely comes down to where their PPA contracts are settled. Nobles 2 has an offtake agreement with a utility, which is typically settled at the node. Through this PPA, Nobles 2 passes on the nodal price risk to the utility and receives a fixed price in return, regardless of how negative the nodal price becomes. In contrast, Caddo has a vPPA with a corporate offtaker, which is typically settled at the hub. If the hub price is significantly higher than the nodal price, which is often the case during periods of congestion, then the project will likely lose money on the vPPA. And if this loss can’t be offset by the PTC value, then the project’s rational response will be to economically curtail. Furthermore, many corporate offtake contracts contain a price floor that caps the buyer’s exposure to negative prices. Thus, projects with a price floor in their offtake contract will only have the PTC value to cushion the blow of negative pricing; once that threshold is crossed, curtailment becomes the only economic option.

The takeaway: Two projects with nearly identical market conditions experience a 6x difference in curtailment purely because of how their contracts allocate nodal price risk. 

The third project in the figure, Moraine Wind, demonstrates how curtailment behavior changes once a project is no longer eligible for the PTC. Without the value of the PTC to offset negative prices, Moraine Wind begins economically curtailing as soon as nodal prices drop below $0/MWh, losing nearly 25% of its overall potential generation due to curtailment. Although this curtailment loss seems extreme, it’s less of an anomaly and more of a preview of what’s to come - as more and more wind projects roll off the PTC, this type of curtailment behavior will become much more common. If you're underwriting an offtake contract or investing in a project without modeling the PTC roll-off date, you're missing the bigger picture of your curtailment risk. 

Key Takeaways

Data from the Curtailment Lens demonstrates that broad regional averages provide a helpful baseline, but curtailment is ultimately decided at the project level by specific contract structures, transmission constraints, and tax credits. Key takeaways for market participants include the following:

• For buyers: Consider both the project’s location and the impact of contract terms on project behavior when assessing curtailment risk, as high amounts of curtailment can put sustainability targets at risk
• For developers: Take current and planned transmission capacity into account when siting projects and consider hedging nodal price exposure with offtake contract terms
• For investors: PTC roll-off introduces an inflection point in curtailment behavior, as older projects are much more likely to curtail than newer projects. Ensure the impact of the PTC is taken into account in your curtailment models

Curious whether your projects look more like Nobles 2 or Caddo Wind? That’s exactly what the Curtailment Lens was built to show, enabling users to view project-level curtailment trends, compare curtailment behavior across projects, and make informed decisions about where to procure, site, or invest in clean energy. To learn more or request a walkthrough, contact our team at [email protected]. 

For more information about our Curtailment Lens, check out our blog: The hidden risk to your portfolio: Unpacking curtailment trends in ERCOT.

REFERENCES

1. ERCOT is the only U.S. market that directly reports hourly plant-level generation. Outside of ERCOT, Resurety derived hourly plant generation by parsing public power market transaction filings. Due to both the difficulty of parsing this information and the limited availability of hourly transactions, the projects in Curtailment Lens currently represent ~50% of operating utility-scale wind and solar projects in MISO, PJM, and SPP
2. https://capitol.texas.gov/tlodocs/88R/handouts/C4502023030810301/74be8cc7-b179-4a83-a59d-c56e8f6db775.PDF
3. https://www.misoenergy.org/planning/transmission-planning/mtep/#t=10&p=0&s=&sd=
4. https://www.spp.org/news-list/spp-board-approves-77-billion-plan-for-transmission-builds-upgrades/
5. https://www.spp.org/western-services/rto-expansion/
6.  As reported in FERC EQR filings
7. https://www.apexcleanenergy.com/news/apex-clean-energy-expands-partnership-with-mcdonalds/ 
8. https://www.novoco.com/news/irs-releases-2026-inflation-adjustment-factor-for-renewable-energy-ptc