Oncor Transmission Service covers transmission, distribution, customer service, and metering. Transmission billing uses ERCOT’s four coincident peaks (4CP). The forecast adds wholesale electricity supply and calculates each charge from grid imports or site capacity.
Service overview
| Item | Coverage |
|---|---|
| Service | Texas · ERCOT · Oncor Transmission Service, schedule 6.1.1.1.7. |
| Supply | Wholesale energy priced separately from Oncor delivery service. |
| Tariff version | August 2026. The forecast excludes the temporary rate update effective October 4, 2026. |
| Transmission billing method | ERCOT four coincident peaks (4CP), applied under Oncor Transmission Service. |
| Billing basis | 15-minute transmission peaks; monthly distribution and fixed charges. Results are in real 2025 dollars. |
| Initial service | The initial forecast calendar year assumes service at full campus nameplate capacity. Later years use coincident peaks. |
The forecast retains the August baseline while the final decision in PUCT Docket 59249 remains pending. September 18 final briefs and the judge’s 60-day timetable point to a proposal for decision by November 17, 2026, if the record-close date is unchanged. The Commission’s final order follows a separate process.
Charge breakdown
| Line item / what it pays for | Tariff Charge Type | How the Charge Is Assessed | Calculation basis |
|---|---|---|---|
| Wholesale electricity supply | Supply | Energy | Imported MWh multiplied by the ERCOT wholesale price. |
| Transmission cost recovery | Transmission | Fixed initially; Energy in later years | Initial forecast calendar year: campus nameplate MW multiplied by annual rate divided by 12 each month. Later years: average imported MW at four summer system peaks multiplied by annual rate. |
| Distribution service and included riders | Distribution | Capacity (demand-based) | Monthly peak imported MW multiplied by the combined distribution and rider rate. |
| Customer service | Distribution | Fixed | Monthly customer amount. |
| Standard metering | Distribution | Fixed | Monthly metering amount. |
How charges are calculated
Electricity supply
Imported energy in each interval is multiplied by the ERCOT wholesale price for that interval.
Supply cost is calculated by multiplying imports in MWh by the price in $/MWh for each interval, then adding the interval costs.
Transmission
Transmission charges recover the cost of the high-voltage network. The initial forecast calendar year uses a fixed monthly assessment based on total campus nameplate capacity:
During initial service, the monthly transmission cost uses campus nameplate MW multiplied by the annual transmission rate in $/MW-year, divided by 12.
In later years, transmission costs depend on imports at four coincident peaks, or 4CP: the highest 15-minute ERCOT system demand in each month from June through September.
Annual transmission cost is calculated by multiplying the average imported MW at the four peaks by the annual rate in $/MW-year.
The Energy assessment applies to imports during those four peak intervals. The forecast uses current-year peaks; utility invoices use prior-year 4CP demand.
Distribution
Distribution charges recover delivery costs through a base demand rate, riders, and credits. They share the monthly maximum grid-import demand:
Monthly distribution cost is calculated by multiplying the highest imported MW in the month by the combined rate in $/MW-month.
| Included charge or credit | Treatment |
|---|---|
| Base distribution service | Escalates using historical base-rate growth. |
| Distribution and historical expense recovery | Follows effective-date rate schedules. |
| Rate-case expense recovery | Assumed to continue from June 2026 through May 2027. |
| Interim credit | Reduces charges during August–December 2026. |
| Interest refunds | Each refund covers one calendar month; midmonth changes are day-weighted. |
| Decommissioning and mobile generation | Follow effective-date rate schedules. |
The combined rate includes these riders and credits. The forecast uses the current monthly peak. The tariff’s demand ratchet can carry forward 80% of a higher peak from the preceding 11 months.
Customer service and metering
Customer service and standard metering are separate fixed monthly charges, each with its own rate escalation.
Forecast methodology
| Charge | How its rate changes |
|---|---|
| Electricity supply | Follows the ERCOT wholesale price forecast. |
| Transmission | Forecast ERCOT transmission costs are adjusted for wholesale recovery. The cost allocated to Oncor’s Transmission Service class is divided by its billing demand to calculate the rate. Recovery and allocation factors stay constant; billing demand follows the assumed growth path. |
| Customer service, metering, and base distribution | Each rate follows its own nominal growth rate, derived from 2018–2026 tariff changes. |
| Distribution riders and credits | Retain their individual recovery periods, effective dates, and refund schedules. |
Nominal charges are converted to real 2025 dollars at the billing-period start. Wholesale and transmission forecasts already expressed in real 2025 dollars retain that basis.
Assumptions and limitations
| Assumption | Effect on results |
|---|---|
| Demand ratchet | Using the monthly peak can understate distribution charges for a declining or curtailed load. |
| Partial periods | Transmission peaks are selected over complete calendar years. Monthly fixed and demand charges are not prorated by service days. |
| Supply contract | Retail-provider premiums and site-specific charges are excluded. |
Public tariffs and regulatory filings
| Source | Coverage |
|---|---|
| Retail Delivery Service tariff | August 2026 basis: schedule 6.1.1.1.7, PDF pp. 80–81; recovery adjustments, pp. 105–108. The linked PDF may be updated. |
| Docket 59249: temporary-rate notice | October 4, 2026 temporary rates, excluded from this forecast baseline. |
| Docket 59249: SOAH Order No. 1 | Page 4: proposal for decision due 60 days after the record closes. |
| PUCT Docket 59046 | Transmission cost recovery filing: class billing demand, allocation, and prior-period credit. |
| PUCT Docket 59080, Staff Matrix B | March 16, 2026 filing, Parameters sheet. Proposed matrix used to calibrate the forecast. |
Methodology version: October 2026. Results use real 2025 dollars.