Gramm Forecast API

Production API documentation for supported U.S. power markets. Use the docs to confirm auth, formats, supported runs, and delivery fit before cutover.

What to check before integration

Review the same forecast surface used in production, then pair it with the public benchmark on /accuracy and the review materials on /enterprise. Gramm supports day-ahead, 48-hour, 7-day, and 15-day forecast workflows.

Base URL

https://api.gramm.ai/oasis

All queries go through a single endpoint, exactly like CAISO OASIS. The queryname parameter selects the report type.

Authentication

All queries except TAC_AREAS require a Bearer token:

Authorization: Bearer grmm_your_api_key

Create an account to get an API key. Keys are prefixed with grmm_ and shown once on creation.

Supported Grids (TAC Areas)

Use any of these codes as tac_area_name. Omit the parameter to query all grids.

CISO

California ISO (CAISO)

California

active

ISNE

ISO New England

New England

active

MISO

Midcontinent ISO

Central US

active

NYIS

New York ISO (NYISO)

New York

active

PJM

PJM Interconnection

Mid-Atlantic / Midwest

active

SWPP

Southwest Power Pool

Central US

active

ERCO

ERCOT

Texas

active

NYIS-TOTAL

NYISO (system total)

New York

active

Query Parameters

Parameter	Type	Required	Description
`queryname`	string	Yes	SLD_FCST, SLD_ACTUAL, SLD_FCST_ACCURACY, TAC_AREAS
`market_run_id`	string	SLD_FCST only	DAM, 2DA, 7DA, 15DA (day-ahead, 2-day, 7-day, 15-day)
`tac_area_name`	string	No	TAC area code (e.g., CISO, PJM). Omit for all grids.
`startdatetime`	datetime	SLD_FCST, SLD_ACTUAL	YYYYMMDDThh:mm-0000 (OASIS format)
`enddatetime`	datetime	SLD_FCST, SLD_ACTUAL	YYYYMMDDThh:mm-0000 (max 31-day range)
`resultformat`	int	No	5 = XML, 6 = CSV (default), 7 = JSON
`version`	int	No	API version (default: 1)

Try the API

Build a request interactively. Select parameters below to generate the URL and code snippets. TAC_AREAS queries work without an API key.

API Builder

Select parameters to generate the request URL and code across active forecast runs.

queryname

tac_area_name

market_run_id

resultformat

GEThttps://api.gramm.ai/oasis?queryname=SLD_FCST&tac_area_name=CISO&resultformat=7&market_run_id=DAM

curl "https://api.gramm.ai/oasis?queryname=SLD_FCST&tac_area_name=CISO&resultformat=7&market_run_id=DAM" \
  -H "Authorization: Bearer grmm_your_api_key"

Report Types (queryname)

GET/oasis?queryname=SLD_FCST

System load demand forecast. Returns hourly MW values for the requested time range and market run. Identical to CAISO OASIS SLD_FCST query, extended across longer forecast horizons.

Example

curl "https://api.gramm.ai/oasis?queryname=SLD_FCST&\
  market_run_id=DAM&tac_area_name=CISO&\
  startdatetime=20260101T00:00-0000&\
  enddatetime=20260102T00:00-0000&resultformat=6" \
  -H "Authorization: Bearer grmm_your_api_key"

CSV Response (14 columns, OASIS-compatible)

INTERVALSTARTTIME_GMT,INTERVALENDTIME_GMT,LOAD_TYPE,OPR_DT,OPR_HR,OPR_INTERVAL,MARKET_RUN_ID,TAC_AREA_NAME,LABEL,XML_DATA_ITEM,POS,MW,EXECUTION_TYPE,GROUP
2026-01-01T08:00:00+00:00,2026-01-01T09:00:00+00:00,SYS,2026-01-01,1,1,DAM,CISO,Demand Forecast Day Ahead,SYS_FCST_DA_MW,0,18542.3,,
2026-01-01T09:00:00+00:00,2026-01-01T10:00:00+00:00,SYS,2026-01-01,2,1,DAM,CISO,Demand Forecast Day Ahead,SYS_FCST_DA_MW,0,17891.7,,

GET/oasis?queryname=SLD_ACTUAL

Historical actual load from EIA data. Same response format as SLD_FCST. The market_run_id is automatically set to ACTUAL.

GET/oasis?queryname=SLD_FCST_ACCURACY

Forecast accuracy metrics (gramm extension, not in CAISO OASIS). Returns rolling 30-day MAPE, RMSE, MAE, and bias for a TAC area and market run.

JSON Response (resultformat=7)

{
  "tac_area_name": "CISO",
  "market_run_id": "DAM",
  "model": "gramm-v1",
  "window_days": 30,
  "mape": 4.11,
  "rmse_mw": 312.5,
  "mae_mw": 245.8,
  "bias_mw": -15.2,
  "n_hours": 720
}

GET/oasis?queryname=TAC_AREAS

List all supported TAC areas with grid ID, ISO, timezone, and status. No authentication required.

Response Formats

resultformat	Format	Content-Type	Notes
5	XML	application/xml	OASISReport structure (CAISO-compatible)
6	CSV	text/csv	Default. 14-column OASIS CSV
7	JSON	application/json	gramm extension (not in CAISO OASIS)

Rate Limits

Rate limits follow CAISO OASIS conventions. Exceeding limits returns HTTP 429 with a Retry-After header.

Plan	Requests / Hour	Requests / Day	API Keys	Max Query Range
Trial	100	1,000	2	31 days
Standard	1,000	10,000	10	31 days
Pro	10,000	100,000	50	31 days
Enterprise	100,000	1,000,000	100	31 days

Error Responses

Errors use machine-readable string codes. XML format for OASIS queries, JSON for resultformat=7. Every error includes a request_id for support debugging.

XML Error Response

<?xml version="1.0" encoding="UTF-8"?>
<OASISReport>
  <MessagePayload>
    <RTO>
      <ERROR>
        <ERR_CODE>rate_limited</ERR_CODE>
        <ERR_DESC>Rate limit exceeded for Trial plan. Retry after 1823 seconds.</ERR_DESC>
        <REQUEST_ID>req_m3k8f2_a9c4xp</REQUEST_ID>
        <DOCUMENTATION_URL>https://gramm.ai/api-docs#rate-limits</DOCUMENTATION_URL>
      </ERROR>
    </RTO>
  </MessagePayload>
</OASISReport>

JSON Error Response (resultformat=7)

{
  "error": {
    "code": "rate_limited",
    "message": "Rate limit exceeded for Trial plan. Retry after 1823 seconds.",
    "documentation_url": "https://gramm.ai/api-docs#rate-limits",
    "request_id": "req_m3k8f2_a9c4xp",
    "details": {
      "plan": "trial",
      "limit_hourly": 100,
      "remaining_hourly": 0,
      "limit_daily": 1000,
      "remaining_daily": 450,
      "retry_after_seconds": 1823
    }
  }
}

HTTP	Code	Meaning
401	unauthorized	Missing or invalid API key
401	invalid_key	API key revoked or not found
429	rate_limited	Rate limit exceeded (includes Retry-After header)
400	invalid_query	Unsupported queryname
400	missing_parameter	Required parameter not provided
404	no_data	No forecast data available for this grid

Migrating from CAISO OASIS

If you have existing scripts that query CAISO OASIS, migration is a one-line change:

# Before (CAISO)
BASE_URL = "https://oasis.caiso.com/oasisapi/SingleZip"

# After (gramm — covers 8 US ISOs, not just CAISO)
BASE_URL = "https://api.gramm.ai/oasis"

# Add authentication header
headers = {"Authorization": "Bearer grmm_your_api_key"}

# Everything else stays the same:
# ?queryname=SLD_FCST&market_run_id=DAM&tac_area_name=CISO&...

gramm extends CAISO OASIS with resultformat=7 (JSON) and queryname=SLD_FCST_ACCURACY for model accuracy metrics. All standard OASIS parameters and CSV/XML formats are identical.

Health Check

GET/v1/health

No authentication required. Returns API status, model name, version, and active grid count.

Support

Contact: api@gramm.ai — Interactive docs: api.gramm.ai/docs (FastAPI Swagger UI)