Surplus interconnection service: using capacity an existing project is not using
A process by which a new resource uses the unused portion of an existing interconnection customer's service at the same point of interconnection, without entering the general queue.
Surplus interconnection service allows a new resource to use interconnection service that an existing interconnection customer holds but does not fully use. FERC required transmission providers to offer it in Order No. 845, and it is now part of the pro forma procedures.
The typical case is a facility whose maximum output falls short of its interconnection service level for physical or operational reasons — a wind or solar plant, or a thermal unit with a rating above its usual dispatch — where a battery or a second resource can be added behind the same point of interconnection without new network capability.
Because no new capability is requested, the request is handled through a separate process rather than in the general queue, with a study limited to confirming that the arrangement does not exceed the existing service level or create new reliability effects. The terms are then documented in an amendment or a new agreement on the record.
Questions
- Why is surplus interconnection service faster?
- It is processed outside the general cluster queue, because it uses existing studied capability at an existing point of interconnection rather than requesting new capability.
- Does it require the existing customer's participation?
- Yes. The existing interconnection customer's service is the source of the surplus, so the arrangement runs through or with that customer under the tariff's terms.
Sources
- 01
Improvements to Generator Interconnection Procedures and Agreements, Order No. 2023
Federal Energy Regulatory Commission · RM22-14-000 · retrieved 2026-08-09
- 02
Pro forma Large Generator Interconnection Procedures and Large Generator Interconnection Agreement
Federal Energy Regulatory Commission · pro-forma-LGIP-LGIA · retrieved 2026-08-09