generated: '2026-07-27'
method: probed
source: >-
  CAISO API Terms of Use (https://www.caiso.com/privacy-terms-of-use#api-terms-of-use)
  plus live 429 responses observed against https://oasis.caiso.com/oasisapi on 2026-07-27
provider: California ISO
providerId: caiso
description: >-
  CAISO publishes no numeric rate limit, quota or burst allowance for the OASIS Download
  API, but it does enforce one at the edge. Its published API Terms of Use prohibit
  "Adverse and Excessive Use" and reserve the right to suspend or terminate access for
  callers who impact system performance. In practice the F5 BigIP in front of
  oasis.caiso.com answers a request that arrives too soon after the previous one with
  HTTP 429 and the plain-HTML body "CAISO Acceptable Use Policy Violation. Please retry
  your request after 5 seconds." — so the operative published limit is the five-second
  spacing named in that response body. This was verified live: two identical, valid
  SingleZip requests issued back to back returned 200 then 429, and the same 429 is
  returned for malformed/parameterless requests to the servlet. No X-RateLimit-* headers
  and no Retry-After header are returned; the retry interval is only in the body text.
  The Today's Outlook CSV feeds under www.caiso.com/outlook are served from the web tier
  and no throttling was observed on them.
algorithm: acceptable-use-policy-throttle
enforcement: edge (F5 BigIP in front of oasis.caiso.com)
responseCodes:
  throttled: 429
headers:
  retry_after: false
  ratelimit_headers: false
  note: >-
    The 429 carries Server: BigIP and a 114-byte HTML body; the retry guidance is in the
    body text only, not in a header.
limits:
- id: oasis-request-spacing
  scope: client-ip
  api: CAISO OASIS Download API
  host: oasis.caiso.com
  limit_count: 1
  limit_interval: 5s
  basis: >-
    Observed 429 body text "Please retry your request after 5 seconds." and reproduced by
    issuing two valid SingleZip requests back to back (2026-07-27).
  documented: false
  verified: true
- id: oasis-date-range-cap
  scope: request
  api: CAISO OASIS Download API
  limit_count: 31
  limit_interval: days-per-request
  basis: >-
    Documented in the Interface Specification for OASIS error table (code 1004, "Data can
    be requested for period of 31 days only") and confirmed live — a PRC_LMP request
    spanning 2024-01-01 to 2026-01-01 returned an in-band 1004 error inside the zip.
    CAISO's OASIS FAQ notes the range cap differs by report; some reports allow a single
    trade day only.
  documented: true
  verified: true
- id: oasis-all-nodes-window
  scope: request
  api: CAISO OASIS Download API
  limit_count: 1
  limit_interval: hour-or-trade-date-per-request
  basis: >-
    OASIS FAQ: when retrieving all nodes with grp_type=ALL the caller may retrieve only
    one hour (interval reports) or one trade date (hourly reports) at a time.
  documented: true
  verified: false
retention:
  window: 39 months
  basis: >-
    OASIS FAQ Question Two — "The OASIS data retention for the majority of the reports
    available is the previous 39 months."
guidance:
- Space OASIS requests at least five seconds apart per source IP.
- >-
  Consult the Publication and Revisions Log and the Publication Schedule reports before
  polling, as recommended in section 4 of the Interface Specification, rather than
  polling blindly for data that has not yet posted.
- >-
  Use GroupZip for whole-day, all-node pulls instead of looping SingleZip per node — the
  spec designates GroupZip for exactly that case.
- >-
  Do not use the API to monitor availability or performance of CAISO systems; the API
  Terms of Use prohibit benchmarking and monitoring use.
sources:
- https://www.caiso.com/privacy-terms-of-use#api-terms-of-use
- https://www.caiso.com/documents/oasis-frequently-asked-questions.pdf
- https://www.caiso.com/documents/oasisapispecification.pdf