The six generation adequacy reports required by the June 18 FERC show cause orders were on the docket by close of business Monday July 20. PJM, MISO, SPP, CAISO, ISO-NE, and NYISO each filed the analytical foundation the Commission asked for. No ISO requested an extension, and the July 20 deadline held across all six proceedings. The 60-day clock on the tariff response now runs to August 17, which is 28 days from Tuesday.
The five categories the Commission named in the June 18 orders structured each filing, but the substantive read across the six is a single ratio. Each generation adequacy report discloses the projected large load additions inside the ISO’s five-year planning horizon and the projected non-large-load additions on the same horizon. The ratio of the two is what the Commission staff will use to gauge whether the existing tariff remains just and reasonable, because a large load pipeline that dominates the load addition profile changes the character of the transmission service the ISO is providing. The 0.5 threshold flagged in the preceding week’s preview is the analytical breakpoint. Filings above 0.5 face a heavier burden defending the existing tariff. Filings below 0.5 can present a narrower, more targeted reform.
The July 20 filings now sort the six ISOs into two clusters against that threshold.
The cluster above 0.5
PJM disclosed the highest ratio of the six. The PJM generation adequacy report projects roughly 62 GW of new large load additions inside the 2026 to 2031 planning horizon against roughly 71 GW of total load additions on the same horizon, for a ratio of 0.87. The 62 GW figure includes the interconnection requests already in the New Services Queue and the specific hyperscaler-anchored projects with signed letters of intent that PJM has taken into its planning model, but excludes speculative requests without a filed application. PJM’s filing frames the ratio as the specific analytical basis for the co-location tariff framework already in flight under the December 18, 2025 order, and the August 17 response will build the Firm Contract Demand and Non-Firm Contract Demand products into an integrated tariff proposal covering the categories the December 2025 order did not fully address.
MISO’s filing came in with a ratio of 0.68. The 28 GW of projected large load additions in MISO’s five-year horizon are concentrated in the MISO North and Central footprints, with specific density in Ohio, Indiana, and Iowa. MISO’s disclosure includes a breakout of the co-location arrangement fraction inside the large load pipeline, which the filing puts at approximately 45 percent of the nameplate. That co-location fraction is the specific input that argues for a co-location tariff product on the August 17 filing. The MISO filing does not commit to a specific product structure, but signals that the response will include a proposed framework rather than a narrower reform, which is the specific question that had been open on the MISO calendar through Q2 2026.
SPP’s filing produced a ratio of 0.58. The absolute nameplate is smaller than PJM and MISO, with roughly 11 GW of large load additions projected against 19 GW of total load additions, but the ratio still crosses the 0.5 threshold. The SPP large load pipeline is concentrated in Oklahoma and the Texas panhandle sites that fall inside the SPP balancing authority area rather than ERCOT. SPP’s filing explicitly names the flexible large load transmission service category from the June 18 order as the category the August 17 response will center on, which signals a tariff product built around a transmission service that is not standard Network Integration Transmission Service, structured to price the large load’s willingness to accept curtailment during peak transmission stress.
The cluster below 0.5
CAISO’s filing produced a ratio of 0.34. The California large load pipeline is smaller in nameplate than the eastern RTOs, with roughly 8 GW of projected large load additions against 24 GW of total load additions, and the ratio reflects the sustained electrification-driven residential and commercial load growth that dominates California’s forecast rather than the large load growth. The CAISO filing frames the smaller ratio as support for a partial defense of the existing tariff, supplemented by narrower reforms on the study process side. The California Public Utilities Commission joined the CAISO filing as a co-signatory, which is procedurally distinctive for a FERC-jurisdictional filing but consistent with the specific split of jurisdiction between the CAISO market and California retail regulation. The August 17 response will most likely propose a study process reform aligned to the CPUC’s parallel proceedings on data center rates and interconnection, rather than a full tariff product for co-located load.
ISO-NE filed a ratio of 0.22. The absolute large load pipeline in New England is small, with roughly 2 GW of projected large load additions against 9 GW of total load additions dominated by electrification and grid-connected heat pump load growth. The ISO-NE filing is the most defensive of the six, framing the existing tariff and the Forward Capacity Market structure as already substantially responsive to the large load integration problem the Commission identified. The specific reform ISO-NE signals is targeted to the Capacity Accreditation Resource process the RTO uses to translate resource characteristics into FCM capacity credits, extended to cover co-located load. That is a narrower reform than the eastern cluster is preparing.
NYISO filed a ratio of 0.29. The New York large load pipeline is comparable to New England’s on a per-capita basis but smaller than New England’s in absolute nameplate, with roughly 1.5 GW of large load additions projected inside the 2026 to 2031 window. The NYISO filing frames the response category around the Installed Capacity market design, where any large load treatment has to interact with the ICAP auction. The August 17 response will most likely propose changes to the ICAP demand curve and the Local Capacity Requirement calculation to incorporate large load, rather than a standalone co-location product. Like ISO-NE, this is a narrower reform than the eastern cluster is preparing.
The reserve margin question
The generation adequacy reports also disclosed the reserve margin implication of the projected large load additions against the projected generation additions. The reserve margin math is the second-order read, and it cuts differently across the two clusters.
PJM’s report projects a reserve margin decline from the current level of approximately 18 percent installed capacity above peak load to approximately 12 percent by the 2029/2030 delivery year if the projected large load additions materialize on schedule and no additional generation is added beyond the current queue. The 12 percent figure is below the PJM Installed Reserve Margin target of 14.7 percent for the 2028/2029 delivery year that cleared July 7, and materially below the target on a forward basis. The reserve margin decline is the specific pressure point that argues for the flexible large load transmission service category on the August 17 response, because a large load that accepts curtailment during peak transmission stress functionally acts as a demand-side reserve.
MISO’s reserve margin projection shows a similar directional pattern with a shallower slope, declining from approximately 17.5 percent to approximately 14 percent over the five-year horizon under the current queue. MISO’s Planning Reserve Margin Requirement for the 2026/2027 planning year is 8.9 percent on a coincident summer basis under the seasonal accreditation methodology, which is not directly comparable to the PJM installed capacity number, but the direction of pressure is the same.
SPP’s reserve margin decline is the steepest of the three eastern filings on a percentage basis, moving from approximately 21 percent to approximately 12 percent over the horizon. The SPP tariff response will need to address the reserve margin question directly, either through a specific procurement mechanism or through a demand-side reserve product tied to the flexible large load transmission service.
CAISO, ISO-NE, and NYISO all show reserve margins that remain above the ISO’s target level under the projected large load additions, which is consistent with the smaller ratios. The reserve margin question is not the operative pressure on the narrower-reform cluster.
What the August 17 responses will look like
Reading the six filings against each other, the August 17 tariff responses will split along the two clusters.
PJM’s response will integrate the Firm Contract Demand and Non-Firm Contract Demand framework already on the record with targeted supplements addressing the efficient study process and the generator-load pairing categories. This is the least uncertain filing of the six.
MISO’s and SPP’s responses will each propose a substantive co-location framework covering multiple categories from the June 18 order. Neither has a filed framework on the record now, which means both filings will be new tariff language rather than integrations of existing filings. The specific structural choice each makes about whether to borrow the PJM Firm and Non-Firm Contract Demand categories directly or to build a distinct product structure will define the co-location procurement math for the eastern non-PJM footprints through the FERC review window.
CAISO’s response will most likely propose a study process reform paired with a CPUC-coordinated retail rate treatment for data center loads, rather than a full FERC-jurisdictional co-location tariff product.
ISO-NE’s and NYISO’s responses will most likely propose targeted reforms inside the FCM and ICAP structures respectively, framed as adaptations of the existing market design rather than new tariff products.
The gap between the two clusters is the specific input for developer siting decisions across the 33 days between Monday’s filings and the August 17 responses. A hyperscaler evaluating a site that could clear into either PJM or MISO is now reading the filings for the specific structural choice each RTO is signaling, because that choice defines the transmission service the site will receive and the reserve product the site will pay into. A hyperscaler evaluating a site in the smaller cluster is reading the filings for the specific narrower reforms each ISO is preparing, which set the interconnection cost and the operating flexibility on a different margin.
Sources
- Federal Energy Regulatory Commission, “FERC Launches Aggressive Targeted Action to Speed Large Load Integration,” news release, June 19, 2026, ferc.gov/news-events/news/ferc-launches-aggressive-targeted-action-speed-large-load-integration.
- Federal Energy Regulatory Commission, Order on Show Cause Proceeding (PJM co-location), Docket EL25-49-000, issued December 18, 2025.
- Clean Power Press, “The July 20 generation adequacy filings in the six FERC 206 show cause dockets are the last dated input before the August 17 tariff response deadline sets the co-location rules for every non-PJM ISO,” July 15, 2026.
- Clean Power Press, “Solar-plus-storage capacity accreditation now splits three ways across PJM, MISO, and ERCOT, and the hybrid ELCC number is what actually anchors the PPA,” July 17, 2026.