Glossary of Terms




Ancillary Service A service necessary to support the transmission of energy to Loads while maintaining reliable operation of the Transmission Service Provider’s (TSP’s) transmission system using Good Utility Practice.
Congestion The situation that exists when requests for power transfers across a Transmission Facility element or set of elements, when netted, exceed the transfer capability of such elements.
Day-Ahead Market (DAM) A daily, co-optimized market in the Day-Ahead for Ancillary Service capacity, certain CRRs, and forward financial energy transactions.
Day-Ahead Reliability Unit Commitment (DRUC) A Reliability Unit Commitment (RUC) process performed for the next Operating Day.
Demand The amount of instantaneous electric power in MW delivered at any specified point or points on a system.
Distributed Generation (DG) An electrical generating facility located at a Customer’s point of delivery (point of common coupling) ten megawatts (MW) or less and connected at a voltage less than or equal to 60 kilovolts (kV) which may be connected in parallel operation to the utility system.
Distribution Losses The difference between the energy delivered to the Distribution System and the energy consumed by Customers connected to the Distribution System.
DUNS Number A unique nine-digit common company identifier used in electronic commerce transactions, supplied by the Data Universal Numbering System (DUNS).
Electric Reliability Council of Texas, Inc. (ERCOT) The organization approved by the Federal Energy Regulatory Commission (FERC) to perform the electric reliability organization functions described in the Electricity Modernization Act of 2005, 16 U.S.C. § 824o (2005).
Electric Service Identifier (ESI ID) The basic identifier assigned to each Service Delivery Point used in the registration and settlement systems managed by ERCOT or another Independent Organization.
Emergency Interruptible Load Service (EILS) A special emergency service consistent with subsection (a) of P.U.C. SUBST. R. 25.507, Electric Reliability Council of Texas (ERCOT) Emergency Interruptible Load Service (EILS), used during an Energy Emergency Alert (EEA) Level 2B to reduce Load and assist in maintaining or restoring ERCOT System frequency. EILS is not an Ancillary Service.
Force Majeur Event Any event beyond the reasonable control of, and that occurs without the fault or negligence of, an Entity whose performance is prevented by the occurrence of such event. Examples of such a Force Majeure Event may include the following, subject to the limitations of the above sentence: an act of God, labor disturbance, act of the public enemy, war, insurrection, riot, fire, storm or flood, explosion, breakage or accident to machinery or equipment, or a curtailment, order, regulation or restriction imposed by governmental, military, or lawfully established civilian authorities.
Interval Data Recorder (IDR) A metering device that is capable of recording energy in each Settlement Interval.
KWH Kilowatt Hour
Load Factor Ratio of average energy demand (load) to the maximum demand (peak load) during a period of time. 

Load Factor is an indicator of how steady an electrical load is over time (ratio of consumption to peak demand).  If your load factor is low, you should look for ways to even out your electrical usage (lower your peak demand).  By increasing load factor, you will reduce the cost of your monthly demand charge and also lower the rate of your per kWh cost.

Load Profile Type A classification of a group of Customers having similar energy usage patterns and that are assigned the same Load Profile.
Locational Marginal Price (LMP) The offer-based marginal cost of serving the next increment of Load at an Electrical Bus, which marginal cost is produced by the DAM process or by the SCED process. 


The price calculated for a Hub for each SCED interval according to the formula in Section, Hub LMPs, using LMPs at the Electrical Buses included in the Hub.

Load Zone LMP

The price calculated for a Load Zone for each SCED interval according to the formula in Section, Load Zone LMPs, using State Estimator (SE) Load data and LMPs at the Electrical Buses included in the Load Zone.

Market Clearing Price for Energy The highest price associated with a Congestion Zone for a Settlement Interval for Balancing Energy deployed during the Settlement Interval.
MWh Megawatt Hour
On-Peak Hours Hours ending in 0700 to 2200 CPT from Monday through Friday excluding NERC holidays.
Provider of Last Resort (POLR) The designated CR as defined in the P.U.C. SUBST. R. 25.43, Provider of Last Resort (POLR), for default Customer service, and as further described in Section 15.1, Customer Switch of Competitive Retailer.
Reliability Unit Commitment (RUC) A process to ensure that there is adequate Resource capacity and Ancillary Service capacity committed in the proper locations to serve ERCOT forecasted Load.
Renewable Energy Credit (REC) A tradable instrument that represents all of the renewable attributes associated with one MWh of production from a certified renewable generator.
Retail Electric Provider (REP) As defined in P.U.C. SUBST. R. 25.5, Definitions, an Entity that sells electric energy to retail Customers in Texas but does not own or operate generation assets and is not an MOU or EC.
Settlement Interval The time period for which markets are settled.
Transmission and/or Distribution Service Provider (TDSP) An Entity that is a TSP, a DSP or both, or an Entity that has been selected to own and operate Transmission Facilities and has a PUCT approved code of conduct in accordance with P.U.C. SUBST. R. 25.272, Code of Conduct for Electric Utilities and Their Affiliates.
Weather Zone A geographic region in which climatological characteristics are similar for all areas within such region.