How it works
PJM's new contract-demand paths and ERCOT's large-load changes can offer earlier energization in exchange for curtailment. The trap: federal emergency-engine rules sharply limit the non-emergency hours you can bank on, and state air permits add their own caps and definitions. In a worked Virginia scenario, that can swing summer deliverable capacity by roughly 20–30%.
The trap
Your interconnection contract is one rule system. Federal RICE NESHAP is a second. Your state air permit is a third. Most developers price the first one when they evaluate a curtailable interconnection offer. Almost nobody prices the interaction.
The interaction is where the project value lives. RICE NESHAP does not let you treat every curtailment hour as ordinary backup runtime. The federal rule carves the year into narrow emergency and non-emergency buckets, and state permits add their own caps, definitions of “emergency,” and guidance memos. When PJM or ERCOT curtails you, the site has to decide in real time whether generator runtime still fits inside those buckets, or whether actual compute load has to come off.
In a worked Virginia scenario, that can swing summer capacity by roughly 20–30%. On a 500 MW site, that is project-defining. And the answer can change when a state DEQ updates its guidance or an ISO changes the product terms.
The math
Illustrative scenario. 500 MW IT load, ~600 MW Tier II diesel fleet (250 × 2.5 MW), Virginia minor-source permit at 500 hrs/yr aggregate, and a modeled 6 PJM curtailment events per year averaging 6 hours each. Federal emergency-engine rules are treated as a binding constraint alongside state permit logic.
Case A · DEQ treats curtailment as an emergency response
Post-APG-578, if the outage notice is 14 days or less and the operator follows DEQ's notice and reporting steps, the modeled 36 curtailment hours can fit inside the site's emergency-treatment assumption. Combined with testing and true outages, the year stays inside the 500-hour aggregate cap.
That avoids a modeled capacity hit, but it can still create major-source and compliance risk. The practical question is not just whether you can run, but which permit tier and cost structure you trigger if you do.
Case B · DEQ treats curtailment as non-emergency
If the curtailment hours do not qualify as emergency operation, the project burns through the narrow federal non-emergency allowances much faster. Under that assumption, the site quickly runs out of generator-backed coverage during repeated summer events.
The practical response is often to shed actual compute load during some events, add cleaner or non-road backup options, or reject the faster non-firm product and wait for firmer service.
The swing: the same site can model near-full coverage or a material summer de-rate, depending on how the federal hour buckets, the state permit, and the interconnection product line up. That is the underwriting problem Cliff is solving.
What we model
The calculator is built on a state-by-state air-permit logic layer that we maintain like an incentive atlas: structured records, weekly refresh, citation per claim, and a versioned changelog every time a state DEQ updates its guidance.
Inputs
Outputs
Why now
FERC's December 2025 co-location order pushed PJM into a paper-hearing process on firm, non-firm, and interim non-firm service. Texas SB 6 is already in force for large loads, and ERCOT's Batch Zero process remains under active stakeholder review in 2026. The decision tree is live.
Live dockets · updated weekly
“A 200 MW interconnection becomes about 85 MW of realized peak after the IT/overhead split and a 3–5 year buildout. That’s a 25–35% structurally stranded reservation gap, before curtailment ever enters the picture.”
“We used to be inside-the-four-walls experts. Now we’ve had to bolt on land enablement, site permitting, air permits, and power generation.”
Why nobody sells this
Federal RICE NESHAP rules are public. PJM and ERCOT tariff language is public. State air permit templates are public. The hard part is the mapping from each state’s emergency definition + standard permit + guidance memos to runtime-hour accounting that survives an EPA audit.
That mapping is fragmented across Virginia DEQ, TCEQ, Ohio EPA, GA EPD, ADEQ, and dozens more. It keeps changing. Most permit advisors still sell this as bespoke project work, and most software stops upstream of the air-permit logic layer.
The wedge isn’t the math. The math is in the rules. The wedge is the data discipline to keep the rules current.
Run the calculator
Site, generator fleet, interconnection product, expected curtailment. The result updates as you type. The full report unlocks with your email.