Your TDU in Texas is determined entirely by your address, and any household can identify it in under two minutes using a ZIP code lookup, a recent electricity bill, or the TDU's own service area tool.

What a TDU Is and Why It Matters

In Texas's deregulated electricity market, two separate companies handle power for most households: a retail electric provider (REP) that sets rates and handles billing, and a transmission and distribution utility (TDU) that physically owns and maintains the wires, poles, meters, and transformers that connect to the home. A household can switch its REP at any time. The TDU, however, is determined by geography and does not change.

The Public Utility Commission of Texas (PUCT) assigns each address within the ERCOT grid to exactly one of four TDUs. This assignment matters for three practical reasons.

First, TDU delivery charges appear as a fixed line item on every electricity bill, regardless of which REP holds the account. These charges are not negotiable and are not included in most advertised rate headlines. As of mid-2025 tariff filings, delivery charges ranged from roughly 3 to 6 cents per kWh depending on territory (PUCT interchange filings).

Second, outage reporting and emergency response run through the TDU, not the REP. Calling the wrong number during a storm wastes time.

Third, some plan availability and pricing structures vary by TDU territory. Knowing the correct territory ensures that any rate comparison reflects plans actually available at the address.

The Four TDUs That Serve Deregulated Texas

ERCOT, the grid operator covering most of the state, oversees the competitive market. Within that grid, four investor-owned utilities hold territorial franchises under PUCT certificates.

Oncor Electric Delivery covers the Dallas-Fort Worth metroplex, West Texas, and a band of smaller communities in between. Oncor is the largest TDU in Texas by customer count, serving approximately 3.7 million metered locations as of 2024 (Oncor 2024 Annual Report). Addresses in Dallas, Fort Worth, Arlington, Plano, Waco, Lubbock, Midland, and Wichita Falls fall within Oncor territory in virtually all cases.

CenterPoint Energy Houston Electric serves the Greater Houston area and surrounding counties. CenterPoint delivers power to approximately 2.8 million customers (CenterPoint 2024 10-K filing). Residents of Houston, Galveston (most of the island), Conroe, The Woodlands, Pasadena, and Sugar Land are typically in CenterPoint territory.

AEP Texas operates across a large portion of South and West Texas, including Corpus Christi, Laredo, Abilene, and San Angelo. AEP Texas serves approximately 1 million customers. The company formerly operated under two names, AEP Central and AEP North, which were consolidated. Residents near Harlingen, Brownsville, McAllen, and Victoria are generally in AEP Texas territory.

Texas-New Mexico Power (TNMP) is the smallest of the four, serving roughly 260,000 customers in areas including parts of the Texas Panhandle, the Rio Grande Valley, Lake Jackson, Clute, Freeport, and portions of Galveston Island not served by CenterPoint. TNMP territory often surprises residents because it appears in patches near larger metro areas rather than one contiguous block.

One important boundary to note: San Antonio (CPS Energy) and Austin (Austin Energy) are served by municipal utilities that operate outside the deregulated ERCOT competitive market. Residents of those cities cannot choose a retail electric provider and do not have a PUCT-regulated TDU in the same sense. This guide applies only to addresses within the deregulated ERCOT footprint.

Three Ways to Identify Your TDU

Method 1: ZIP Code Lookup on PowerToChoose.org

The fastest method for most households is entering a ZIP code on PowerToChoose.org, the official PUCT plan comparison site. The site filters plan results by TDU territory automatically. After entering a ZIP, the assigned TDU appears in the filter panel alongside available plans.

This method works reliably for the majority of addresses. A small number of ZIP codes straddle two TDU territories, typically in rural areas or near the edges of metro service areas. If the site returns results for more than one territory, proceed to Method 2 or Method 3 for a definitive answer.

Method 2: Read a Recent Electricity Bill

Every Texas electricity bill must itemize TDU delivery charges as a separate line under PUCT Substantive Rule 25.474. Look for a section labeled "Transmission and Distribution" or "TDU Delivery Charges." The TDU's legal name appears there explicitly, typically alongside a PUCT certificate number.

This method is definitive because it reflects the actual metered account, not a ZIP code approximation. A household with a bill on hand can confirm its TDU in about 30 seconds. The REP's name on the front page of the bill is not the TDU. The TDU name appears only in the delivery charge breakdown.

Method 3: Address Search on the TDU's Own Website

Each TDU offers an address-level service area verification tool:

  • Oncor: oncor.com, under the outage center or service territory section
  • CenterPoint: centerpointenergy.com, address lookup in the Texas residential section
  • AEP Texas: aeptexas.com, service area map and address search
  • TNMP: tnmp.com, service territory page

Entering a full street address in the relevant tool returns a direct yes or no. This is the most reliable approach for addresses near territory boundaries, new construction not yet reflected in ZIP databases, or rural routes where ZIP codes span multiple territories.

TDU Delivery Charges: What to Expect by Territory

Knowing a TDU territory allows a more accurate interpretation of any rate quote. TDU delivery charges are pass-through costs. REPs collect them on behalf of the TDU and are not permitted to mark them up (PUCT Substantive Rule 25.474). The charges appear in every plan's Electricity Facts Label (EFL) and are included in the effective rate shown at 500, 1,000, and 2,000 kWh.

As of mid-2025 tariff filings, approximate monthly delivery charge structures were:

  • Oncor: roughly $3.42 monthly customer charge plus $0.0358 per kWh
  • CenterPoint: roughly $4.39 monthly customer charge plus $0.0440 per kWh
  • AEP Texas: approximately $5.00 to $7.00 monthly customer charge plus $0.035 to $0.045 per kWh, varying by sub-territory
  • TNMP: approximately $7.18 monthly customer charge plus $0.0307 per kWh

These figures shift when TDUs file rate cases with the PUCT. For current tariff schedules, the PUCT interchange database at interchange.puc.texas.gov allows searches by TDU name under filed tariff documents.

A household in TNMP territory pays a higher fixed customer charge but a lower per-kWh delivery rate than a comparable household in CenterPoint territory. At 1,000 kWh of usage, the effective monthly delivery cost is similar across territories, but the structure favors different usage profiles differently.

Why the TDU Does Not Change When Switching Plans

Switching retail electric providers does not change the TDU. When a household enrolls in a new plan through PowerToChoose.org or any other channel, Oncor, CenterPoint, AEP Texas, or TNMP continues to own the meter and the line to the home. Only the billing and rate relationship changes.

During storms or outages, the TDU handles repair regardless of which REP is on the account. The outage reporting number belongs to the TDU. If a household calls its REP about a power outage, the REP will redirect the call to the TDU.

When Switching Is Not Worth It

Identifying a TDU is the first step in plan comparison, not the last. A household should also pull its 12-month usage history (available through the TDU's Green Button data portal), check whether an existing contract carries an early termination fee, and compare EFLs at the usage level that matches actual consumption rather than the advertised headline rate.

If a current contract's early termination fee exceeds the projected savings over the contract's remaining term, switching before the contract ends will cost more than it saves. The practical move in that case is to note the contract end date and begin comparing plans 30 to 60 days before expiration, when switching is free and rates can be locked before the contract lapses onto a default variable rate.