generated: '2026-07-27'
method: searched
source: >-
  NYISO Metering API User Guide and NYISO Finance APIs User's Guide v1.2 DRAFT
  for the REST surfaces; live anonymous probes of mis.nyiso.com/public and
  oasis-postings.nyiso.com on 2026-07-27 for the file surfaces
docs: https://www.nyiso.com/manuals-tech-bulletins-user-guides
summary: >-
  NYISO has two entirely separate sets of conventions because it runs two
  entirely separate kinds of interface. The public data surfaces are file
  archives addressed by a stable, date-templated URL convention with no query
  language, no pagination and no authentication. The market-participant REST
  APIs are JSON-over-HTTPS with URI-path versioning, ISO-8601 Eastern-offset
  timestamps, fixed decimal precision, an all-or-nothing validation model on
  writes and a client-supplied plus server-supplied request-id pair for tracing.
  Neither surface documents an idempotency key, a rate limit, a pagination
  cursor or a field-expansion mechanism.

surfaces:

- surface: MIS public data archive
  base_url: http://mis.nyiso.com/public
  style: date-templated file archive
  auth: none
  formats: [csv, pdf, zip, htm, txt, xls]
  url_convention:
    daily: /public/csv/<report-dir>/<YYYYMMDD><report-name>.csv
    monthly_bundle: /public/csv/<report-dir>/<YYYYMM01><report-name>_csv.zip
    current_snapshot: /public/csv/<report-dir>/current<ReportName>.csv
    static_reference: /public/csv/<report-dir>/<report-name>.csv
    parallel_renderings: >-
      Many reports publish the same content under /public/pdf/<report-dir>/ and
      some under /public/htm/ or /public/txt/ using the same date prefix.
    index_pages: /public/<report-code>list.htm (for example P-2Alist.htm), catalogued from /public/menu.htm
  examples_verified_2026_07_27:
  - http://mis.nyiso.com/public/csv/damlbmp/20260726damlbmp_zone.csv
  - http://mis.nyiso.com/public/csv/rtfuelmix/20260726rtfuelmix.csv
  - http://mis.nyiso.com/public/csv/pal/20260726pal.csv
  - http://mis.nyiso.com/public/csv/isolf/20260726isolf.csv
  - http://mis.nyiso.com/public/csv/damlbmp/20260701damlbmp_zone_csv.zip
  time_semantics: >-
    Timestamps are rendered MM/DD/YYYY HH:MM[:SS] in Eastern clock time, not
    ISO-8601. Reports that carry a Time Zone column emit EST or EDT explicitly;
    reports that do not (day-ahead LBMP, ISO load forecast) leave the daylight
    saving transition ambiguous and must be reconciled against the calendar.
  identifiers: >-
    Locations are identified by NYISO PTID (integer point identifier) alongside a
    short zone or generator Name. PTIDs are resolvable against the Generator
    Names (P-19), Load Names (P-20) and Active Transmission Nodes (P-66) reference
    files.
  pagination: none - one file per report per day; range retrieval is done by
    iterating dates or downloading the monthly ZIP bundle
  rate_limits: none documented and none observed; be a good citizen and prefer
    the monthly ZIP bundle over iterating daily files for backfills
  error_handling: >-
    A file that does not exist returns 404 (verified - a daily-named ZIP returned
    404 where only the monthly-named ZIP exists). There is no error envelope.
  schemas: >-
    NYISO publishes no schema document. API Evangelist derived JSON Schemas for
    ten of the highest-traffic reports from live header rows - see json-schema/.

- surface: OASIS postings
  base_url: https://oasis-postings.nyiso.com
  style: anonymously listable object store
  auth: none
  url_convention:
    dated: /<POSTING_TYPE>/<FORMAT>/<YYYY>/<MM>/<DD>/<name>-<YYYYMMDD>.csv
    static: /<POSTING_TYPE>/<FORMAT>/<name>.csv
    listing: GET / returns an S3 ListBucketResult in application/xml
  formats: [csv, html, pdf]
  notes: >-
    History reaches back to 1999. The human front end at oasis.nyiso.com is a
    single-page application; NAESB WEQ-001 template-interface paths were probed
    and returned the SPA HTML shell, so no template interface is claimed.

- surface: Finance APIs and Metering API
  base_url: https://api.nyiso.com
  style: JSON over HTTPS, resource-per-path
  media_type: application/json
  request_headers_documented:
    Accept: application/json
    Accept-Encoding: gzip, deflate
    Authorization: Basic encodedCredential
    Cache-Control: no-cache
    Content-Type: application/json
  versioning:
    scheme: uri-path
    current: v1
    example: https://api.nyiso.com/finance/metering/v1/powerMetering
    note: >-
      A second, unrelated "version" concept exists in the payload - the invoice
      version number of settlement data, a number with one decimal place where 0
      means "latest".
  authentication: see authentication/nyiso-authentication.yml
  date_time:
    standard: ISO-8601
    month: yyyy-MM
    date: yyyy-MM-dd
    datetime: yyyy-MM-ddTHH:mm:ssX
    timezone: >-
      Requests may use any valid ISO-8601 offset; responses are always rendered
      in Eastern time with an explicit offset (-05:00 EST, -04:00 EDT). End of a
      period must be expressed as :59:59, e.g. 2021-12-14T23:59:59-05:00.
  numeric_precision:
    mwh: up to four decimal places
    dollars: two decimal places
  query_conventions:
    range_selection: >-
      Either billingMonth (yyyy-MM) or a startTime/endTime (or startDate/endDate)
      pair - mutually exclusive on most operations. endTime/endDate are
      inclusive. Invoicing caps a date range at 31 days.
    repeatable_filters: >-
      PTID filters (genPtid, tiePtid, subzonePtid, busPtid) may be repeated as
      URL parameters; a meterDataType parameter narrows to ALL, GENERATOR, TIE or
      SUBZONE, defaulting to ALL.
    version_parameter: >-
      An optional version parameter selects an invoice version of settlement
      data; 0 (the default) returns the latest.
  pagination:
    supported: false
    note: >-
      No cursor, offset, page or limit parameter is documented. Response size is
      bounded by the time range and PTID filters the caller supplies, and by the
      three-year-and-ten-month availability window.
  field_expansion:
    supported: false
  sparse_fields:
    supported: false
  metadata:
    supported: false
  request_tracing:
    client_supplied: >-
      userRequestId - optional, max 30 characters, letters/numbers/hyphens/
      underscores. Supplied on submission inside submissionParameters or as a
      query parameter on retrieval, and echoed back in the response.
    server_supplied: >-
      nyisoRequestId - a UUID returned on every submission response, alongside
      requestTimestamp.
    header_based: none - tracing is carried in the JSON body, not in headers
  idempotency:
    supported: false
    note: >-
      No Idempotency-Key header or equivalent is documented. Writes are instead
      all-or-nothing at the request level - if any record in a submission fails
      validation the entire request is rejected - and submissions are stated to
      cover "both new entries and updates" for a given point and service hour,
      so a repeated submission of identical data overwrites rather than
      duplicating. That is upsert behaviour, not a published idempotency
      contract, and it is recorded here as absent rather than inferred as
      present.
  dry_run:
    supported: true
    note: >-
      submissionParameters.doNotCommit (Metering API guide) / doCommit (Finance
      APIs guide v1.2) validates a submission without storing any record -
      described by NYISO as designed primarily for testing. See
      sandbox/nyiso-sandbox.yml.
  error_envelope: see errors/nyiso-problem-types.yml
  rate_limits:
    documented: false
    note: No rate limit, quota or throttling behaviour is documented in either guide.
  data_availability_window: >-
    Three years and ten months ending with the current month, for metering,
    settlements and invoicing retrieval.

cross_links:
  authentication: authentication/nyiso-authentication.yml
  errors: errors/nyiso-problem-types.yml
  lifecycle: lifecycle/nyiso-lifecycle.yml
  sandbox: sandbox/nyiso-sandbox.yml
  data_model: data-model/nyiso-data-model.yml
  json_schema: json-schema/