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Press Release

Valuing Transmission Congestion Rights (TCRs) in ERCOT

For congestion pricing, the ERCOT region is divided into four zones, namely the
North, West, South and the Houston zones, and five Commercially Significant
Constraints (“CSCs”) inter-zonal interfaces. The inter-zonal congestion is
usually managed using (1) balancing energy, because it is effective and
efficient, or (2) unit-specific deployments of local generators.

ERCOT market participants who transact business across congestion zones can
hedge congestion charges in the balancing energy market by acquiring
Transmission Congestion Rights (“TCR”). A TCR or Pre-assigned Congestion Rights
(“PCRs”) represents the cost of one MW (Shadow Price) flowing in one direction
on a CSC during a particular hour over a given time period. Both TCRs and PCRs
entitle the holder to payments corresponding to the inter-zonal congestion

ERCOT determines the number of available TCRs based on the summer peak flow
limits for the CSCs and offers them at annual and monthly auctions while some
TCRs are pre-assigned to certain Non Opt-in entities (NOIEs), such as municipal
utilities and cooperatives, at 15% of the auction clearing price, because of
long term contractual obligations.

In 2008 the TCR annual auction prices are significantly lower than the value of
congestion in real-time due to the inability of participants to forecast the
inter-zonal congestion costs accurately.

Recently ERCOT completed an analysis of load flow data to determine the expected
operating limits and CSC constraints using the Steady State Working Group (SSWG)
data set which was developed by ERCOT using UPLAN electricity model.

2009 CSCs

In 2008 the West to North CSC was frequently congested and was binding in 5,320
intervals (15 percent). The primary reason for the high frequency of congestion
on the West to North CSC in 2008 is the significant increase in installed wind
generation relative to the load in the West Zone and limited transmission export
capability to the broader market.

For 2009 ERCOT Board has approved five transmission interfaces as CSCs for the
four commercial pricing zones. These CSCs are summarized below.

  • CSC # 1 (West to North) and CSC # 5 (North to West) are defined as the
    following lines:

    • Graham – Cook Field 345 kV

    • Jacksboro – Bowman 345 kV

    • Graham – Tonkawa 345 kV

    • Bowman – Graham 345 kV

    • Commanche Switch – Red Creek 345 kV

    • Graham – Long Creek 345 kV

  • CSC # 2 (South to North) and CSC # 3 (North to South):

    • Temple - Lake Creek 345 kV

    • Temple Pecan Creek – Tradinghouse 345 kV

  • CSC # 4 – North to Houston

    • Singleton- Obrien 345 kV

    • Singleton – TH Wharton 345 kV

LCG Offering

ERCOT establishes the CSC limits across all the interfaces every 15 minutes and
publishes for each interface the limits as well as the actual flow. LCG has
analyzed the changes in the limits for all the five CSCs and their correlations and from these data, developed a number of Significant Scenarios of Interface Limits
(SSIL) of all the CSCs and used UPLAN model to simulate 8760 hours of ERCOT
operations for each CSC interface.

These simulation results are used to calculate the TCR values and their are provided to the participants in terms of market heat rates so that participants can convert them into monetary values using their own view of the fuel prices.


  • Summary of input assumptions of the ERCOT system including generation,
    loads, fuel prices and transmission 

  • Annual and monthly TCR values for each of the five interfaces

  • The average, standard deviation and volatility of the TCR values

  • Histogram of the TCR values for all CSCs

  • The average, standard deviation and volatility of peak and off-peak
    zonal prices (in implied heat rate)

  • Two hours' consultation

Note that there is a discrepancy between the TCR auction values and the
real-time zonal prices due to forecasting errors. LCG can simulate both
real-time (nodal) and day-ahead markets using UPLAN to estimate auction values.


Participants interested in obtaining annual and/or monthly TCR projections for
2010 may contact Julie Chien at 650-962-9670x110 or send email to to talk to our TCR specialists.

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Database of Plants, Loads, Assets, Transmission...
Annual summary of prices, congestion and important events in ERCOT
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