Register for ISO-NE Web Services access at https://www.iso-ne.com/participate/support/web-services-data; ISO customers and non-participants can apply for automated data access using the REST interface at the base URL https://webservices.iso-ne.com/api/v1.1.
Authenticate using HTTP Basic Auth with your ISO-NE web services username and password included in the Authorization header; all requests must be made over HTTPS.
Retrieve five-minute real-time LMPs for a specific node by calling GET /v1.1/fiveminutelmp/current/location/{locationid}; replace {locationid} with the ISO-NE location ID for the desired pricing node — retrieve the full node list from GET /v1.1/locations/all.
The response is available in both XML and JSON — request JSON by adding the Accept: application/json header; the response contains an array of FiveMinuteLmp objects each with BeginDate, LocationId, LmpTotal, EnergyComponent, CongestionComponent, and LossComponent.
For historical five-minute data, use GET /v1.1/fiveminutelmp/day/{date}/location/{locationid} where {date} is in YYYYMMDD format; this returns all 5-minute intervals for the specified operating day.
Implement polling at an interval aligned with the data publication cadence (approximately every 5 minutes for real-time data); use the BeginDate timestamp to detect duplicate or out-of-order records and dedup before inserting into your time-series store.
Known gotchas
ISO-NE Web Services uses HTTP Basic Auth, not OAuth; storing credentials in environment variables or a secrets manager is essential — do not hardcode them or log the Authorization header in application logs.
ISO-NE location IDs are integers and differ from the human-readable location names (e.g., 'HQ_P1_P2-1' for a specific interface point); always retrieve the location list and map IDs to names before presenting data to users.
The ISO-NE Web Services Business Documentation Spreadsheet (updated periodically, with a July 2025 revision noted) is the authoritative reference for all available endpoints and parameters; the spreadsheet is available on the ISO-NE website and should be consulted when adding new data feeds rather than relying solely on the API swagger documentation.
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