If you live in Oncor's service area and looked closely at your August electricity bill, you may have noticed something odd. The per-kWh delivery charge line on your bill actually went down. Yet the bottom line came in higher than July. A typical 1,000-kWh Texas home saw about $2.73 more. This is not a billing error, and it is not your Retail Electric Provider padding a rate. Two separate PUCT-approved rate changes hit Oncor territory on August 1, 2026, and they moved in opposite directions.

Here is what changed, why it happened, how long it lasts, and what Ambit Energy customers and other Texas households can and cannot do about it.

Key takeaways

• Oncor's published per-kWh delivery rate dropped by $0.000901/kWh on August 1, 2026, from $0.061196 to $0.060295.
• On the same day, a new PUCT-approved temporary surcharge called Rider IS started at $0.003633/kWh for residential customers.
• At 1,000 kWh, the math is: minus $0.90 from the lower delivery rate, plus $3.63 from Rider IS, for a net increase of $2.73 per month.
• Rider IS is temporary. It ends by the last billing cycles of December 2026.
• Every Retail Electric Provider in Oncor's territory bills these same charges. Switching providers does not remove them. What you can shop is the energy charge and the plan structure.

The Three-Line Reconciliation: how to check the math on your own bill

Because two Oncor changes took effect on the same day, and one moved down while the other moved up, the fairest way to read your August bill is to reconcile them line by line. We call this the Three-Line Reconciliation. You need three numbers.

1. Your July per-kWh Oncor delivery charge: $0.061196/kWh.
2. Your August per-kWh Oncor delivery charge, which is the new base tariff of $0.060295/kWh plus Rider IS at $0.003633/kWh. Add these to get the true August delivery number: $0.063928/kWh.
3. Your monthly kilowatt-hour usage from the meter read on your bill.

Multiply your usage by both per-kWh numbers, subtract, and you have the exact dollar change on your bill from the Oncor side. For 1,000 kWh, that equation lands at plus $2.73. At 1,500 kWh, closer to plus $4.10. At 750 kWh, closer to plus $2.05. The fixed customer and metering charges did not change, so those stay at $4.06 per month combined.

This reconciliation only covers the delivery side of your bill. Anything else that moved between July and August, including your energy charge or usage change, is separate.

What actually changed on August 1 for Oncor delivery

The base delivery tariff quietly moved down. According to the Public Utility Commission of Texas monthly TDU rate report, Oncor's residential combined volumetric delivery charge dropped from $0.061196 per kWh in July 2026 to $0.060295 per kWh in August 2026, a decrease of $0.000901 per kWh, or about $0.90 per month for a 1,000-kWh home. The fixed charges stayed at $1.48 for the customer charge and $2.58 for the metering charge, totaling $4.06 per month.

On the surface, this looks like relief. It is real relief, but it is small, and it was more than offset by the second change on the same date.

What is the Rider IS interim surcharge?

The second August 1 change was a new PUCT-approved temporary surcharge called Rider IS, short for Interim Surcharge. It sits on the delivery side of your bill and lives inside the Oncor charges your Retail Electric Provider passes through. For residential customers, Rider IS adds $0.003633 per kWh. At 1,000 kWh, that is $3.63 per month.

Do the math against the $0.90 drop and you land at $2.73. That is where the number in the headline comes from.

Rider IS is not a hidden add-on. Every Retail Electric Provider in Oncor's territory is required to bill it, and every REP receives the same instruction from Oncor and the PUCT. The rider amount does not vary by REP or by plan. It varies by usage and by rate class.

For small commercial customers, the rider changes shape based on the rate class filed at the PUCT:

• Secondary service at 10 kW or below: $0.002878 per kWh.
• Secondary service above 10 kW: $0.997891 per billing kW.
• Primary service at 10 kW or below: $0.059827 per kWh.
• Primary service above 10 kW: $0.908924 per billing kW.
• Primary substation: $0.130513 per billing kW.
• Lighting service: $0.048697 per kWh.

If you run a small business in Oncor's territory, walk your July bill through your applicable Rider IS rate to size the impact before your next renewal window opens.

What is PUCT Docket 58306, and why is this happening?

Rider IS did not appear from nowhere. It came out of Oncor's most recent comprehensive base-rate case at the Public Utility Commission of Texas, filed as Docket 58306.

Here is the timeline.

According to Oncor (2026), the company filed the base-rate review on June 26, 2025, initially seeking about $834 million in additional annual revenue. According to the Texas Coalition for Affordable Power's April 2026 analysis, the negotiated settlement cut that ask by more than 30 percent. The Public Utility Commission approved the settlement on April 17, 2026, producing a $560 million annual revenue increase, or roughly $274 million less than Oncor originally requested. According to a legal briefing on the approved order (2026), the settlement set Oncor's base-rate revenue requirement at $6.975 billion, which is about an 8.8 percent increase in total electric delivery revenues. Rate-case reference filings from 2026 show the authorized return on equity at 9.75 percent, the authorized common equity ratio at 43.5 percent, and the authorized rate base at $26.45 billion.

The new base rates from Docket 58306 became effective for bills rendered on and after June 1, 2026. That is why your June and July bills already carried some of the change.

Why did the surcharge start August 1 if the rates started June 1?

Because it takes several months to move a big rate case through PUCT proceedings. During January through May 2026, Oncor billed under the old rates while the new ones were still being decided. Once the settlement was approved and the new June 1 rates took effect, there was a gap between what Oncor had collected from January to May and what the approved rates would have generated over the same window.

Rider IS is the PUCT-approved way to close that gap. According to Oncor's second-quarter 2026 earnings materials, the interim surcharge is designed to recover about $212 million of deferred revenue through the end of 2026, reconciling the January 1 through May 31 period against the new June 1 base rates.

How long will Rider IS last?

Rider IS runs through the last billing cycles in December 2026. It is not a permanent increase, and it does not renew on its own. Once the deferred revenue is recovered, the rider comes off and your August delivery-side math resets to the underlying tariff.

For a Texas household using 1,000 kWh per month across August through December, Rider IS adds about $18 in total across the rest of 2026. At 1,500 kWh, closer to $27. For a small business drawing 3,000 kWh, closer to $43.

What are DCRF, TCRF, and EECRF on my bill?

Rider IS is one of several rate mechanisms that let Oncor recover specific costs between full base-rate cases. Three others already sit on your bill.

The Distribution Cost Recovery Factor, or DCRF, recovers Oncor's investment in local distribution wires, poles, and transformers between rate cases. It is filed and updated periodically at the PUCT.

The Transmission Cost Recovery Factor, or TCRF, recovers Oncor's investment in high-voltage transmission lines that move power across the ERCOT grid. In August 2026, the residential TCRF sits at about $0.016932 per kWh in the published rate stack.

The Energy Efficiency Cost Recovery Factor, or EECRF, funds PUCT-approved energy efficiency programs. In August 2026, the residential EECRF sits at about $0.000766 per kWh.

All four riders, including Rider IS, are pass-through charges. Every Retail Electric Provider in Oncor's territory bills the same rider amounts on the same billing lines. For a walkthrough of every TDU line item on a Texas bill, see TDU Delivery Charges Explained.

Can switching your Retail Electric Provider avoid the increase?

No. This is the most misunderstood part of the Texas deregulated market, so it is worth stating plainly. Every Retail Electric Provider in Oncor's territory bills the exact same TDU delivery charges, including the exact same Rider IS amount. Switching does not remove them, hide them, or discount them. A REP can present them line by line, roll them into an all-in rate, or move them into a bill message. The dollars are the same either way.

What you can shop is the energy charge, the plan structure, and the way monthly base fees fit your specific usage. If you use a heavier volume, a lower per-kWh energy charge can outweigh a slightly higher monthly base fee. If you use less, the opposite math often holds. The best way to compare is to read the Electricity Facts Label at your typical usage level, not the marketing headline. For a step-by-step walkthrough, see How to Read Your Texas Electricity Facts Label.

What Texas households can actually control this fall

Because the delivery-side change is fixed and universal, the parts of your bill worth attention are the parts you actually choose.

• Your plan type. Fixed-rate plans lock the energy charge for a term. Variable-rate plans move with the market and often move higher in Texas summers. For the current forward curve read, see Should Texans Lock In a Fixed-Rate Electricity Plan This August.
• Your contract length. Longer terms usually price cheaper per kWh but reduce flexibility, and early termination fees vary by plan.
• Your usage pattern. If your household concentrates use in specific windows, a free-nights or free-weekends plan can win the math, but only when the on-peak rate is competitive. See TXU Free Nights and Weekends vs Ambit Free and Clear Nights for the break-even work.
• Your Electricity Facts Label. Read all six numbers at 500, 1,000, and 2,000 kWh. A plan that looks good at 2,000 kWh can look bad at 500 kWh, and vice versa.

Ambit Energy plan details, availability, and pricing vary. Rates and terms shown are as of publication and subject to change. See the current Electricity Facts Label for full terms and check pricing as of your enrollment date. Enrollment is subject to credit approval and plan availability. Earnings vary and are not guaranteed. Average earnings and savings depend on individual usage, plan selection, and market conditions.

Frequently asked questions

Did Oncor's delivery charges change on August 1, 2026?

Yes. The published per-kWh delivery rate dropped from $0.061196 to $0.060295, a decrease of $0.000901 per kWh. On the same day, a new temporary Rider IS surcharge started at $0.003633 per kWh for residential customers. Net effect at 1,000 kWh: plus $2.73 per month.

What is Rider IS on my Oncor bill?

Rider IS is the Interim Surcharge that the Public Utility Commission of Texas approved as part of Docket 58306, Oncor's most recent base-rate case. It closes the gap between what Oncor collected under the old rates from January through May 2026 and what the approved rates would have generated during the same window. It is temporary.

When will the Oncor interim surcharge end?

Rider IS runs through the last billing cycles in December 2026. It is a temporary reconciliation, not a permanent increase.

Do all Retail Electric Providers bill the same Oncor charges?

Yes. Every REP in Oncor's territory is required to pass through the same TDU delivery charges, including Rider IS. The energy charge, base fees, and plan terms are what actually vary between providers.

Does this apply to small businesses too?

Yes, but the numbers vary by rate class. Secondary customers at 10 kW or below pay Rider IS at $0.002878 per kWh. Above 10 kW, it moves to a per-kW demand charge of $0.997891 per billing kW. Walk your July bill through your rate class before your renewal.

Where can I read the source documents?

The Oncor base-rate case sits in the PUCT Interchange under Docket 58306. The current TDU rate report is published monthly by the Public Utility Commission of Texas. Oncor also posts its retail delivery service tariff on the company's regulatory page.