Market Participant Data

The <MarketParticipantData> section is the same regardless of the dataset being passed in the XML file and is applicable to both Inbound requests and Outbound responses.

Item Description MRTU(CAISO) TX(ERCOT)
Region Control Area/ISO short name (XSD Required) ISO Required Field
Data Type: Enumeration
‘MRTU’
ISO Required Field
Data Type: Enumeration
‘TX’
MarketParticipant Participant short name (XSD Required) ISO Required Field
Data Type: String
‘SC ID’
ISO Required Field
Data Type: Positive Decimal (0)
‘ERCOT QSE ID’
MarketStage Market Stage (XSD Required) ISO Required Field
Data Type: Enumeration
‘DA’
‘RT’
ISO Required Field
Data Type: Enumeration
‘DART’
'SASM'*
FirstIntervalBegin First interval of bilateral schedule (XSD Required) From First Interval Begin to Last IntervalEnd can not span more than 25 hours ISO Required Field
Data Type: XML dateTime (GMT) using Z
e.g. 2025-01-29T00:00:00Z
ISO Required Field
Data Type: XML dateTime (GMT) using Z
e.g. 2025-01-29T00:00:00Z
LastIntervalEnd Last interval of bilateral schedule (XSD Required) From First Interval Begin to Last IntervalEnd can not span more than 25 hours ISO Required Field
Data Type: XML dateTime (GMT) using Z
e.g. 2025-01-29T00:00:00Z
ISO Required Field
Data Type: XML dateTime (GMT) using Z
e.g. 2025-01-29T00:00:00Z

*RTC+B - With the implementation of the RTC+B market change, ERCOT grandfathered the Supplementary Ancillary Service Markets (SASMs: SASM, SASM1…SASM9). Thus, in support of the RTC+B market change, the APX MarketSuite will not allow upload of the SASM bidOffers past December 2025

In MRTU, when the ProductType = Energy or Non Firm Energy and the TxType = Gen, Import or Export, the sum of the DA awarded and self scheduled MWh carry over to RT as a self schedule for each hour. Any RT API or UI submission that occurs prior to the auto carryover (which occurs immediately after the CAISO DA Market Awards file is loaded into the APX scheduling database at approx. 1:00 PM PT) will prevent the

auto-carryover from affecting that specific combination of Location, Product Type, and Interval. Any RT API submissions that occur after the auto carryover (which will be the most common use case) will replace the values that were automatically carried over. For all other ProductType(s), the RT API data submissions are completely separate from the DA.

APX encourages FirstIntervalBegin and LastIntervalEnd range to cover an operating day, hour, or settlement interval. This range cannot exceed 25 hours. To represent an entire operating day for a region operating under Pacific Standard Time (PST), FirstIntervalBegin = ‘2025-03-01T08:00:00.000Z’ and LastIntervalEnd = ‘2025-03-02T08:00:00.000Z’ (FirstIntervalBegin is close ended (>=) and LastIntervalEnd is open ended (<)).