ERCOT Market Overview¶

The Electric Reliability Council of Texas operates the electricity grid for approximately 90% of Texas's load. ERCOT is unique among US ISOs in that it is electrically isolated from the Eastern and Western Interconnections, which means it is not subject to FERC jurisdiction over wholesale markets (though it is regulated by the Public Utility Commission of Texas).

Market Structure¶

ERCOT operates a two-settlement system:

Day-Ahead Market (DAM): Hourly financial commitments cleared the day before the operating day.
Real-Time Market (RTM): 15-minute settlement intervals reflecting actual dispatch conditions.

15-Minute RT Intervals

Unlike MISO and SPP (which use 5-minute RT intervals), ERCOT settles real-time at 15-minute granularity. This affects how RT prices are aggregated to hourly data in ProgridPy.

Settlement Point Types¶

ERCOT prices are published at "Settlement Points" rather than nodes. The SettlementPointType enum in ProgridPy captures the full taxonomy:

Hubs¶

Type	Description
`HU`	Hub -- a weighted average of a group of resource node prices
`SH`	South Hub
`AH`	Houston Hub (weighted average)

Load Zones¶

Type	Description
`LZ`	Load Zone
`LZEW`	Load Zone Energy Weighted
`LZ_DC`	DC Tie Load Zone
`LZ_DCEW`	DC Tie Load Zone Energy Weighted

Resource Nodes¶

Type	Description
`RN`	Resource Node
`LCCRN`	Load Carrying Capacity Resource Node
`PCCRN`	Peak Capacity Carrying Resource Node
`PUN`	Private Use Network

DST and Timestamp Handling¶

ERCOT source files are local-time-based and include a DSTFlag column to disambiguate repeated hours during daylight saving transitions.

DSTFlag Is Required for Correct Processing

During the fall-back transition, hour ending 2 occurs twice. The DSTFlag distinguishes the first occurrence (DST in effect) from the second (standard time). ProgridPy resolves the local delivery date/hour with the DSTFlag, converts to interval_start_utc, and then derives interval_start_local from UTC. This ensures repeated hours have distinct UTC keys.

Processing Flow¶

Parse the local delivery date and hour-ending from the source file.
Use the DSTFlag to resolve DST ambiguity.
Convert the resolved local instant to interval_start_utc.
Derive interval_start_local from interval_start_utc (the final local timestamp preserves the intended wall-clock hour).

Available Raw Data Types¶

Data Type	Description	Granularity
`SPP_DAY_AHEAD_HOURLY`	DA Settlement Point Prices	Hourly, per settlement point
`SPP_REAL_TIME_15_MIN`	RT Settlement Point Prices	15-minute, per settlement point
`AS_PRICES`	Ancillary Service Prices	Hourly, system-wide
`HOURLY_WIND_POWER_PRODUCTION`	Wind generation	Hourly, per resource
`HOURLY_SOLAR_POWER_PRODUCTION`	Solar generation	Hourly, per resource
`LF_BY_MODEL_WEATHER_ZONE`	Load forecast by weather zone	Hourly
`ACTUAL_SYSTEM_LOAD_BY_WEATHER_ZONE`	Actual load by weather zone	Hourly

Processed Data Granularity¶

Processed Type	Description	Typical Rows/Day
`NODAL`	Per-settlement-point DA and RT prices	nodes x 24
`SYSTEM`	System-wide aggregate data	24
`WEATHER_ZONE`	Data partitioned by weather zone	zones x 24
`LOAD_ZONE`	Data partitioned by load zone	zones x 24

Data Access¶

ERCOT publishes data through a public API managed via the ercot_api module within ProgridPy. The ERCOT API uses endpoint-based access with pagination support, unlike the file-browser portals used by SPP and MISO.

from progridpy.iso import ERCOT, ERCOTRawDataType

ercot = ERCOT()
files = ercot.download_raw_data(
    start_date="20250101",
    end_date="20250107",
    data_types=ERCOTRawDataType.SPP_DAY_AHEAD_HOURLY,
)