In competitive retail areas of Texas, TDU (transmission and distribution utility) charges—also called TDSP delivery charges—pay for the poles, wires, transformers, and meters that deliver electricity to your home. Your retail electric provider passes these regulated fees through without markup. The Public Utility Commission of Texas approves the rates.
Residential TDU charges are usually calculated as a flat monthly fee plus a per-kilowatt-hour usage charge: monthly TDU fee + (per-kWh TDU rate × billed kWh). Direct Energy’s customer help page gives the same formula and an example for CenterPoint at 1,000 kWh. Because part of the charge scales with usage, the TDU line on your bill can change from month to month even when your energy price is fixed. Rates also typically adjust at least twice a year (often around March and September).
Source: Direct Energy — Understanding your TDSP charges
Image: Residential electrical service entrance in Arizona, photo by Rsparks3, CC0, via Wikimedia Commons.