What is an Electric Service Identifier (or ESI ID)-

In the state of Texas, an ESI ID is a 17 or 22-digit number used to identify a unique point of electric service delivery to a premise (your home or business). You can find this on your bill as well. (Also see Understanding your electricty bill below)

Variable Rate

A price per KWh that is not guaranteed by a contract, as in a month to month rate. This rate is subject to the energy market or up to the REP. It can go up as high as the REP wishes or go down. This is a very risky energy situation for the consumer.

Transmission and Distribution Utility (TDSU or TDSP)

This is the private company that is responsible for transmission and distributions in your city. There are six companies in Texas. They are divided up by the region they serve. In the Dallas/ Fort Worth area, the TDSU (Transmission and Distribution Utility) is called ONCOR. In the Corpus Christi area the TDSU is called AEP (American Electric Power). Also known as a LDC (Lines Distribution Company) or a LDU (Line Distribution Utility).

Transmission and Distribution

The actual delivery of electricity over poles and wires to your home or business from the power generation facility. These services are provided to you by your local wires company, which is responsible for maintaining the poles and wires, and responding to emergencies and power outages as always. The PUC still regulates transmission and distribution to ensure the safety and reliability of your electric service.

Terms of Service

The contract between a Retail Electric Provider and the customer that outlines fees, length of service and other important information.


Switching electric service without a customer’s approval. This practice is illegal and penalties are enforced by the PUC.

Residential Customer

One of three commonly used customer classes. The other two are commercial and industrial. Residential customers include private households that utilize energy for such needs as heating, cooling, cooking, lighting and small appliances.

REP (Retail Electric Provider)

A company that sells electricity to customers. All Retail Electric Providers must be certified to do business by the Public Utility Commission of Texas. A REP is not mandated to a set energy price. The original purpose of the REP was to utilize competition to lower rates in Texas. The REP sends customers their bills. They do not service the electric lines or produce the power.

In essence, the Retail Electric Provider is, in fact, an Aggregator as the REP joins two or more parties into a single purchasing unit and negotiates with the Energy Producers for electricity. REPs do not generate, nor deliver electricity to their customers. However, the PUC has determined that an Aggregator is something different.

Renewable Energy

Electricity that is made from “environmentally friendly” fuel resources, such as wind, water, biomass or solar. Sometimes referred to as “green” energy. Information on a Retail Electric Provider’s generation sources can be found on its Electricity Facts Label.


Electric providers in Texas are regulated by the Public Utility Commission of Texas (or PUCT). The Public Utilities Commission which regulates privately-owned utilities in the state of Texas. They create the rules that govern the players in the Utilitiy industry including Retail Electric Providers. They issue licenses to these organizations and have the legal ability to fine them for illegal business practices.  The PUCT It is headquartered in the William B. Travis State Office Building at 1701 North Congress in Austin, Texas. They can be reached at 1-888-782-8477. Their website address is http://www.puc.texas.gov/

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