Every large generator filing an interconnection request under the FERC pro forma procedures has to tick one of two boxes on the very first form. The pro forma Large Generator Interconnection Procedures put it plainly in Section 3.2: "At the time the Interconnection Request is submitted, Interconnection Customer must request either Energy Resource Interconnection Service or Network Resource Interconnection Service."
That box determines which studies get run, which network upgrades get assigned to you, how long you wait, and — in the markets with a capacity construct — whether your project can earn capacity revenue at all. It is also the single most commonly misunderstood choice in the queue, because both services sound like they deliver power somewhere and neither of them does.
What NRIS means, in the tariff's own words
Start with the definitions, because the acronyms are misleading.
Energy Resource Interconnection Service (ERIS), per the LGIP definitions section, "shall mean an Interconnection Service that allows the Interconnection Customer to connect its Generating Facility to the Transmission Provider's Transmission System to be eligible to deliver the Generating Facility's electric output using the existing firm or nonfirm capacity of the Transmission Provider's Transmission System on an as available basis. Energy Resource Interconnection Service in and of itself does not convey transmission service."
Network Resource Interconnection Service (NRIS) "shall mean an Interconnection Service that allows the Interconnection Customer to integrate its Large Generating Facility with the Transmission Provider's Transmission System (1) in a manner comparable to that in which the Transmission Provider integrates its generating facilities to serve native load customers; or (2) in an RTO or ISO with market based congestion management, in the same manner as Network Resources. Network Resource Interconnection Service in and of itself does not convey transmission service."
Read those two sentences next to each other and the first myth dies. Neither service is transmission service. Section 3.2.1.1 says ERIS "does not in and of itself convey any right to deliver electricity to any specific customer or Point of Delivery," and Section 3.2.2.2 says exactly the same thing about NRIS. Interconnection gets you connected. Moving the power to a buyer is a separate transmission service request, and being deliverable for resource-adequacy purposes is, in several markets, a third thing again.
So what does NRIS buy? Section 3.2.2.1: NRIS "allows Interconnection Customer's Large Generating Facility to be designated as a Network Resource, up to the Large Generating Facility's full output, on the same basis as existing Network Resources interconnected to Transmission Provider's Transmission System, and to be studied as a Network Resource on the assumption that such a designation will occur."
That is the whole difference, and it is a difference about studies and upgrades, not about rights.
The two studies are not the same test
The service you pick decides what the transmission provider models.
Under ERIS, Section 3.2.1.2 says the study "consists of short circuit/fault duty, steady state (thermal and voltage) and stability analyses." The short-circuit analysis identifies the interconnection facilities and the network upgrades needed to handle fault duty. The stability and steady-state work identifies the upgrades needed "to allow full output of the proposed Large Generating Facility" and also identifies "the maximum allowed output, at the time the study is performed, of the interconnecting Large Generating Facility without requiring additional Network Upgrades."
That last clause is the one to circle. An ERIS study can legitimately conclude: you may connect, and here is the number of megawatts you can push before the system cares. Above that, you are curtailed. ERIS is, by construction, an as-available product.
Under NRIS, Section 3.2.2.2 sets a materially harder test. The study "shall assure that Interconnection Customer's Large Generating Facility meets the requirements for Network Resource Interconnection Service and as a general matter, that such Large Generating Facility's interconnection is also studied with Transmission Provider's Transmission System at peak load, under a variety of severely stressed conditions, to determine whether, with the Large Generating Facility at full output, the aggregate of generation in the local area can be delivered to the aggregate of load on Transmission Provider's Transmission System."
Three things are being asked there that ERIS never asks. The system is at peak load, not at a convenient dispatch. The conditions are severely stressed, meaning contingencies. And the test is aggregate: not can your plant get out, but can the whole local pocket of generation get out to the whole load with your plant running flat. The tariff adds that the approach "assumes that some portion of existing Network Resources are displaced by the output of Interconnection Customer's Large Generating Facility" — you are not being added to the stack, you are being substituted into it.
A harder test finds more constraints. More constraints mean more network upgrades assigned to your project, a larger cost allocation, and usually a longer study cycle. That is the price of NRIS, and it is the entire reason developers ask whether they can avoid it.
You can ask for both, once
The LGIP anticipates the hedge. Section 3.2 continues: "any Interconnection Customer requesting Network Resource Interconnection Service may also request that it be concurrently studied for Energy Resource Interconnection Service, up to the point when an Interconnection Facility Study Agreement is executed. Interconnection Customer may then elect to proceed with Network Resource Interconnection Service or to proceed under a lower level of interconnection service to the extent that only certain upgrades will be completed."
The interconnection request form itself carries the checkbox: "Check here only if Interconnection Customer requesting Network Resource Interconnection Service also seeks to have its Generating Facility studied for Energy Resource Interconnection Service."
In practice this is the default posture for a project whose offtake is not yet nailed down. You get both study results, you see the delta in network-upgrade cost, and you make the ERIS-versus-NRIS call with a number in front of you instead of a guess. The deadline is real, though: the election has to happen before the facilities study agreement is executed. After that you are taking whichever service you are in.
When ERIS is the right answer
ERIS is the right answer more often than its reputation suggests.
When the market pays you for energy, not capacity. ERCOT is the obvious case — there is no centralised capacity market to be deliverable into, so the capacity-accreditation argument for NRIS evaporates. Most of what a merchant wind or solar project in West Texas is selling is energy and ancillary services.
When your offtake is a hedge, not a resource-adequacy contract. A bank PPA or a virtual PPA that settles financially at a hub does not need your plant to be designated a Network Resource. It needs your plant to generate.
When the NRIS upgrade bill would kill the project. This is the common one. A cluster study comes back with a network-upgrade allocation under NRIS that is a multiple of the ERIS number, because the peak-load, severely-stressed, aggregate-delivery test found a constraint two buses away. Dropping to ERIS can turn a dead project into a financeable one — at the cost of accepting congestion risk you now own.
When storage is doing the arbitrage. A battery earning on price spread and ancillary services is exposed to congestion either way; paying for firm deliverability to arbitrage a node can be poor economics.
When NRIS is worth the study
When a capacity market or an RA obligation is the revenue. In PJM, ISO-NE, NYISO and MISO, capacity revenue depends on being accredited, and accreditation depends on the deliverability posture that NRIS establishes. A project financed on capacity revenue that holds only ERIS is financed on a revenue stream it cannot bid into.
When California is the market. CAISO layers its own construct on top: Full Capacity Deliverability Status and Partial Capacity Deliverability Status are allocated out of Transmission Plan Deliverability, and the allocation is competitive and annual. The ISO's 2025 Transmission Plan Deliverability Allocation Report shows how tight that is: summing the ISO's own candidate table, 84 parked Queue Cluster 14 projects sought 22,627 MW of interconnection service capacity, alongside 49 Energy Only projects seeking 5,768 MW — all competing for whatever TPD the annual transmission plan created. In several study areas the report records that no deliverability could be allocated at all. In CAISO, ERIS-equivalent status is not a cheap route to deliverability; it is a queue for a later, contested allocation.
When the long-term buyer is a load-serving entity. An LSE procuring to meet a resource-adequacy requirement generally needs the resource designated. If your counterparty's obligation is an RA obligation, your service level is part of their compliance.
The mistakes that cost real money
Treating NRIS as a delivery guarantee. It is not, and the tariff says so twice. Congestion between your point of interconnection and your point of delivery is still yours. NRIS buys you a study standard and the upgrades that standard demands; it does not buy you a path.
Treating ERIS as free. ERIS still allocates network upgrades — the short-circuit and stability work under Section 3.2.1.2 finds real facilities. ERIS is cheaper, not costless.
Missing the election window. The concurrent-study election closes at execution of the facilities study agreement. Teams that plan to "decide later" find later has already happened.
Assuming the regional tariff matches the pro forma. It frequently does not. Every RTO has filed deviations, and the FERC generator interconnection docket history is largely a record of those deviations being litigated. Order No. 845 (163 FERC ¶ 61,043) added, among other things, the ability to request interconnection service below generating capacity — a lever that changes the ERIS/NRIS calculus for over-built solar and for hybrids. Read your region's Appendix, not the pro forma, before you file.
Forgetting that affected systems are studied on ERIS terms. In recent reform, FERC has directed affected-system transmission providers to study affected-system interconnection requests using ERIS modelling standards, on the reasoning that interconnection is separate from deliverability. If a neighbouring system is studying you, it is probably not studying you as a Network Resource on its side.
How to make the call
A workable sequence:
- Name the revenue. Write down which dollars need deliverability. If the answer is "none of them," ERIS is your baseline.
- Request NRIS with concurrent ERIS study. It costs you optionality nothing and buys you the cost delta as a real number.
- Diary the election deadline against the facilities study agreement date, not against a vague quarter.
- Price the curtailment. If you drop to ERIS, model the congestion at your node from historical locational prices — live nodal prices by market are the starting point, and the historical shape matters more than any single hour.
- Check the regional deliverability construct separately. In CAISO, TPD allocation is its own annual contest with its own affidavit; NRIS-equivalent status does not hand it to you.
The headline, for anyone who reads nothing else: NRIS means your plant gets studied, and upgraded, as though it will be designated a Network Resource. ERIS means it gets connected and takes what the system has spare. Neither one delivers a megawatt-hour to a buyer.
Related on this site
- Getting ahead of CAISO's deliverability window — why the 2026 cycle does not exist, and what that does to a Cluster 15 schedule
- Live grid conditions by market — load, fuel mix and nodal prices across eight operators
- US power plant directory — every operating plant on EIA-860M, by fuel and by state