# California ISO (CAISO)

> The California Independent System Operator operates the high-voltage transmission grid serving roughly 80 percent of California plus a portion of Nevada, and runs the wholesale day-ahead and real-time electricity markets, the Western Energy Imbalance Market (WEIM) and the Extended Day-Ahead Market (EDAM). Two of its interfaces are open to anyone with no key and no account: the OASIS Download API (wholesale market data) and the Today's Outlook CSV feeds (five-minute grid telemetry). Everything else CAISO runs is behind PKI client certificates sponsored by a company User Access Administrator.

Generated by API Evangelist from https://github.com/api-evangelist/caiso — CAISO does not publish an llms.txt of its own (https://www.caiso.com/llms.txt returns 404).

## What you can call anonymously

- [CAISO OASIS Download API](https://www.caiso.com/systems-applications/developer-portal): Servlet-style query interface at `https://oasis.caiso.com/oasisapi`. `SingleZip` returns one report, `GroupZip` returns a whole-day bundle. Every response is a ZIP containing CIM XML (`resultformat=5`) or CSV (`resultformat=6`). No key, no token, no account.
- [CAISO Today's Outlook Data Feeds](https://www.caiso.com/todays-outlook): Plain CSV at `https://www.caiso.com/outlook/current/{report}.csv` and `https://www.caiso.com/outlook/history/{YYYYMMDD}/{report}.csv`, five-minute resolution. Confirmed reports: `fuelsource`, `demand`, `netdemand`, `co2`. Telemetry-based summaries — they do not tie out to the market-based numbers in OASIS.

## Calling rules an agent must respect

- Space OASIS requests **at least five seconds apart**. Too-fast requests get `HTTP 429` with the body `CAISO Acceptable Use Policy Violation. Please retry your request after 5 seconds.` — enforced at the edge, no `Retry-After` header.
- **Errors come back as HTTP 200.** A failed report still returns a ZIP; the error is an `ERR_CODE`/`ERR_DESC` block inside the XML. Unzip and inspect the payload — do not branch on the status line. Codes 1000–1016 are catalogued in `errors/caiso-error-codes.yml`.
- **All datetimes are GMT**, in the form `yyyymmddTHH:MM-0000`. A California trade day is normally `T07:00-0000` to `T07:00-0000`.
- `version` is **per report**, not global — CAISO's own current examples use `version=1`, `version=2` and `version=12`.
- Date ranges are capped (error 1004: 31 days), all-node pulls are capped to one hour or one trade date, and most reports retain the previous **39 months**.
- Use `GroupZip` for whole-day, all-node pulls instead of looping `SingleZip` per node.
- The API Terms of Use prohibit using the API to monitor CAISO system availability or performance, and prohibit excessive use that degrades CAISO systems.

## Example requests (verified 2026-07-27)

- Demand forecast: `https://oasis.caiso.com/oasisapi/SingleZip?queryname=SLD_FCST&market_run_id=DAM&resultformat=6&startdatetime=20260720T07:00-0000&enddatetime=20260721T07:00-0000&version=1`
- Day-ahead LMP for one node: `https://oasis.caiso.com/oasisapi/SingleZip?queryname=PRC_LMP&startdatetime=20260720T07:00-0000&enddatetime=20260721T07:00-0000&version=1&market_run_id=DAM&node=LAPLMG1_7_B2&resultformat=6`
- Renewables forecast: `https://oasis.caiso.com/oasisapi/SingleZip?resultformat=6&queryname=SLD_REN_FCST&version=1&market_run_id=DAM&startdatetime=20260720T07:00-0000&enddatetime=20260721T07:00-0000`
- Whole-day all-node DAM LMP bundle: `https://oasis.caiso.com/oasisapi/GroupZip?groupid=DAM_LMP_GRP&startdatetime=20260720T07:00-0000&version=1&resultformat=6`
- Fuel mix right now: `https://www.caiso.com/outlook/current/fuelsource.csv`

## CAISO documentation

- [Developer portal](https://www.caiso.com/systems-applications/developer-portal)
- [Interface Specification for OASIS (PDF, v3.04)](https://www.caiso.com/documents/oasisapispecification.pdf) — the report catalog, parameters and error codes. Last revised 2010; still the reference for query names.
- [OASIS Frequently Asked Questions (PDF)](https://www.caiso.com/documents/oasis-frequently-asked-questions.pdf) — kept current; the working API examples live here.
- [OASIS user interface](https://oasis.caiso.com/mrioasis/logon.do) — build a query in the UI, then copy the generated download URL as an API template.
- [Developer site signup](https://developer.caiso.com/_login/developersignup.aspx) — required to read the specifications (corporate email domain plus written justification); **not** required to call the API.
- [API Terms of Use](https://www.caiso.com/privacy-terms-of-use#api-terms-of-use)
- [Getting started](https://www.caiso.com/getting-started) · [Glossary](https://www.caiso.com/glossary) · [Business Practice Manuals](https://www.caiso.com/library/business-practice-manuals)
- [Release planning](https://www.caiso.com/systems-applications/release-planning) · [Notices](https://www.caiso.com/notices) · [Energy Matters blog](https://www.caiso.com/about/news/energy-matters-blog)

## API Evangelist artifacts for this provider

- [apis.yml](https://raw.githubusercontent.com/api-evangelist/caiso/refs/heads/main/apis.yml)
- vocabulary/caiso-oasis-query-names.yml — the full report, group and parameter registry
- conventions/caiso-conventions.yml — request shape, timezone, packaging, versioning
- errors/caiso-error-codes.yml — error codes 1000–1016 plus the 429 throttle
- rate-limits/caiso-rate-limits.yml — the five-second spacing and range caps
- authentication/caiso-authentication.yml — anonymous public tier vs PKI participant tier
- examples/caiso-oasis-examples.yml — verified request/response pairs
- lifecycle/caiso-lifecycle.yml · changelog/caiso-changelog.yml · conformance/caiso-conformance.yml
- packages/caiso-packages.yml — community clients only; CAISO ships no SDK

## What does not exist

No OpenAPI, AsyncAPI, GraphQL, MCP server, webhook or event surface. No JSON. No first-party SDK or CLI. No `/.well-known/` documents, no `llms.txt`, no Postman collection, no status page, no SLA, no deprecation policy, no bug bounty or vulnerability disclosure program, and no publicly reachable sandbox — the documented market-simulation host `oasismktsim.caiso.com` no longer resolves. No Green Button, ESPI or consumer-usage surface exists, and none should be expected: CAISO is a wholesale operator with no retail customers.