Fixed rate electricity plans in Texas have to charge the same price in every billing period of the term, with exactly three exceptions written into the Public Utility Commission of Texas (PUCT) rule that defines them, 16 TAC 25.475(b)(5): actual changes in TDU delivery charges, changes to ERCOT or Texas Regional Entity administrative fees, and new costs imposed by law. A possible fourth, grid reserve costs, is now under review in PUCT Project 59997.

That fourth path isn't new, and it has never been used. The same rule already lets the PUCT designate a specific ancillary service as a cost beyond a provider's control for existing contracts. The one petition the commission has decided under that sentence, for a reserve product called ECRS, was denied in December 2024. On November 5, 2026, PUCT Staff asked whether the path should be repealed, rebuilt with clear rules, or used for ERCOT's newest reserve product, DRRS. Comments are due December 4, 2026. Nothing has been decided.

Key takeaways

• Under 16 TAC 25.475(b)(5), a Texas fixed rate product runs at least three months, and its price, including all recurring charges and ancillary service charges, stays the same every billing period except for three listed causes.
• The three causes are actual TDU delivery charge changes, ERCOT or Texas Regional Entity administrative fee changes, and new or modified fees or costs from federal, state or local law that are beyond the provider's control.
• Grid reserve (ancillary service) costs can't move a fixed price today. That takes an express PUCT designation of a specific ancillary service product, and none has ever been granted. The one petition decided, for ECRS in Docket 55959, was denied on December 19, 2024.
• In Project 59997, PUCT Staff asked on November 5, 2026 whether to repeal that designation path or define a process for using it, starting with ERCOT's new Dispatchable Reliability Reserve Service (DRRS). Comments are due December 4, 2026 and reply comments December 18, 2026.
• ERCOT estimates DRRS will be fully implemented in mid-2028, according to an October 29, 2026 PUCT staff memo. A 12-month fixed plan signed in November 2026 ends before that estimate. A 24-month or 36-month plan runs past it.

What does a fixed rate actually lock in on a Texas electricity plan?

A fixed rate locks in the total price for each billing period of the contract term, not just the energy charge. The PUCT's definition of a fixed rate product in 16 TAC 25.475(b)(5) covers "all recurring charges and ancillary service charges," and the term must be at least three months.

Two other parts of the same rule shape what "fixed" means on a Texas electricity bill:

• 25.475(b)(8) defines price to exclude state and local sales taxes and the reimbursement for the state miscellaneous gross receipts tax, so those can still appear as separate lines.
• 25.475(c)(1)(A)(i) bars a retail electric provider (REP) from using the term "fixed" to market a plan that doesn't meet the definition.

A fixed rate is not a fixed bill. The price holds, but the bill still rises and falls with the kilowatt-hours you use. If you're still choosing between plan types, Fixed-Rate vs Variable-Rate Electricity in Texas covers that decision. This article is about what can still move after you sign.

What are the three reasons a Texas fixed rate can still change?

The rule lets a fixed price vary from the disclosed amount for three reasons only, and anything outside them stays locked for the term. In the words of 25.475(b)(5), the price may vary "solely to reflect actual changes in TDU charges, changes to the Electric Reliability Council of Texas (ERCOT) or Texas Regional Entity, Inc. administrative fees charged to loads or changes resulting from federal, state or local laws that impose new or modified fees or costs on a REP that are beyond the REP's control."

1. TDU delivery charges

TDU delivery charges are the fees your local wires utility, such as Oncor, CenterPoint, AEP Texas or TNMP, bills through your provider to move power to your meter. They are the exception most Texans actually see, because every provider in a territory bills the same delivery charges and a fixed plan can pass a change straight through.

The most recent large example is Oncor. Its residential delivery charge rose from 6.0295 to 6.8673 cents per kWh on October 4, 2026, about $8.38 more at 1,000 kWh a month (as of October 4, 2026), under PUCT Docket 59249. Oncor's fixed monthly charges stayed at $4.06. Those rates are temporary until the PUCT issues a final order, as the Oncor delivery charge breakdown explains. For every territory's line items, see TDU Delivery Charges Explained, and for TNMP's September steps and December surcharge, see the TNMP rate guide.

2. ERCOT and Texas Regional Entity administrative fees

ERCOT, the grid operator for most of Texas, funds itself through a system administration fee charged per megawatt-hour of load, and a change in that fee is the second allowed reason. Texas Regional Entity, which monitors reliability standards in the ERCOT region, is named in the same clause.

This exception is usually tiny. The PUCT approved changing ERCOT's System Administration Fee from $0.63 to $0.61 per MWh, effective January 1, 2026, according to ERCOT's 45-day market notice. One MWh is 1,000 kWh, so on a 1,000 kWh month that change is $0.02.

3. New fees or costs imposed by law

The third reason covers changes from federal, state or local laws that impose new or modified fees or costs on a REP that are beyond the REP's control. It needs a law, not a market move, which makes it the narrowest of the three in day-to-day practice.

One word-level detail is worth knowing. The indexed product definition right below it, 25.475(b)(6), adds "or regulatory actions" to the same exception. The fixed rate definition leaves those words out and handles grid reserve costs in a separate sentence of its own, which is where Project 59997 comes in.

The Fixed-Rate Exception Map

This table puts every possible cause side by side, with the latest real case for each and its size on a 1,000 kWh month.

Can grid reserve costs raise a fixed rate in Texas today?

No. Ancillary service costs are already part of a Texas fixed price, and the rule says the price "may not vary from the disclosed amount to reflect changes in ancillary service charges unless the commission expressly designates a specific type of ancillary service product as incurring charges beyond the REP's control for a customer's existing contract." No ancillary service product has ever received that designation.

Ancillary services are the reserves ERCOT buys so the grid can cover a sudden loss of a power plant or a fast swing in demand. Retail providers pay their share of those costs. Because a fixed price includes ancillary service charges by definition, the cost risk of reserves sits with the provider for the length of a fixed term.

The designation sentence is the one opening the rule leaves. It is written narrowly: a specific type of ancillary service product, an express commission designation, and existing contracts only.

Has the PUCT ever let a fixed rate change for a new reserve product?

No. The only petition the PUCT has decided under the designation sentence was denied. In Docket 55959, the Texas Energy Association for Marketers and the Alliance for Retail Markets filed a joint petition on December 8, 2023, asking the commission to designate ERCOT Contingency Reserve Service (ECRS) so providers could make a one-time adjustment to certain existing fixed-rate contracts. The PUCT issued its declaratory order on December 19, 2024, and the answer was no.

The request covered fixed-rate contracts signed on or before June 9, 2023. According to EnergyChoiceMatters' report of the decision, the PUCT found providers had adequate notice that ECRS was coming. The final order said ERCOT's ECRS procurement in 2023 totaled 2,531 MW, "which was within the estimated range of 1,093 MW and 3,039 MW that ERCOT provided to the Wholesale Market Working Group in 2022."

Commissioners Lori Cobos and Kathleen Jackson voted to deny the petition. Chairman Thomas Gleeson and Commissioner Courtney Hjaltman were recused. The final order did not adopt an administrative law judge's broader proposed conclusion that "there is no question that REPs have a significantly greater ability to [accurately predict A/S costs] than their residential and small commercial customers," so the larger question of who should carry new reserve costs was left open.

The Retail Electric Provider Coalition filed a motion for rehearing on January 13, 2025. On January 22, 2025, the commission voted not to add it to an open meeting agenda.

What is DRRS, and why is the question back in front of the PUCT?

DRRS, short for Dispatchable Reliability Reserve Service, is a new ancillary service ERCOT is building under Nodal Protocol Revision Request 1309. ERCOT's NPRR1309 page says the change "develops Dispatchable Reliability Reserve Service (DRRS) as a new Ancillary Service," and records PUCT approval on July 9, 2026, "as presented in Project No. 54445."

Before that vote, the Retail Electric Provider Coalition asked for order language designating DRRS as a service "that will incur costs beyond the REPs' control at the time that service is incorporated into the ERCOT Ancillary Services plan," EnergyChoiceMatters reported. The July order left that language out, and the PUCT said it would open a project instead.

At the July open meeting, PUCT Chair Thomas Gleeson said he didn't know when the commission would move forward, adding, "I don't think there are lot of details around how that would be done, safeguards for customers, and the like," according to the same EnergyChoiceMatters report. He recommended a project "to see what changes need to be made, what details or guardrails need to be put around this," and tied the issue to the commission's concern with "affordability."

That project is Project 59997. Staff filed the control request on July 15, 2026, and on October 28, 2026 the project was restyled "Treatment of DRRS and Other Future Ancillary Services Costs in Existing Fixed-Rate Retail Contracts."

DRRS isn't running yet. ERCOT estimates DRRS will be fully implemented in mid-2028, according to an October 29, 2026 PUCT staff memo, which says ERCOT's project management office gave that estimate at an October 2026 Protocol Revision Subcommittee meeting. The same memo says DRRS "must also be considered in ERCOT's 2028 AS Methodology development so that quantities may be determined." ERCOT's own comments for its June 2026 board vote also said "Implementation in 2028." No DRRS cost per kWh has been published.

What did the PUCT ask on November 5, 2026?

On November 5, 2026, PUCT Rules & Projects Staff filed questions for comment in Project 59997, and one option on the table is removing the ancillary-service path from the fixed rate rule altogether. Comments are due December 4, 2026, and reply comments are due December 18, 2026. Staff hasn't proposed a rule change, and nothing has been decided.

The Staff memo, from Luisa Venegoni of Rules & Projects, asks stakeholders to address these open questions, as summarized in the memo and in EnergyChoiceMatters' November 5 report:

1. Whether to "Repeal the relevant language in §25.475(b)(5), to eliminate the avenue through which a REP could change the price of an existing fixed-rate contract to reflect ancillary service costs."
2. Whether the PUCT should clearly define a process for considering and authorizing variations to existing fixed-rate contracts to reflect the cost of a new ancillary service.
3. If the provision stays, how the PUCT should designate a qualifying service: a contested case started by providers, part of adopting the new service, or a rulemaking or other proceeding "that establishes criteria in advance to guide the Commission's determination (e.g., a required showing, trigger date, guardrails on the amount or duration of an adjustment)."
4. What standard should apply, whether "beyond the REP's control" is enough by itself, and what notice affected customers should get.
5. For DRRS, at what point "control" over the cost should be deemed established, including: "What circumstances, if any, would prevent a prudent REP from managing DRRS costs through hedging and other risk management practices?"
6. If a variation were allowed, whether it should be a one-time adjustment or a recurring pass-through, and "How should the adjustment or pass-through amount be quantified?"
7. What additional customer protections to order, and whether to settle DRRS after any rule change or through an interim process.

Staff's questions run in both directions. Some would close the path for good. Others would write the rules for using it.

The Office of Public Utility Counsel (OPUC), the state agency that represents residential and small commercial consumers, filed a notice of participation on November 9, 2026. As of November 13, 2026, the project lists four filings, and OPUC's notice is the most recent.

Does DRRS overlap your fixed-rate contract term?

Only the longer terms do, based on ERCOT's current estimate. A 12-month fixed plan signed in November 2026 ends in November 2027, before mid-2028. A 24-month plan ends in November 2028 and a 36-month plan in November 2029, so both run past the estimated DRRS start.

The Term Overlap Check

Overlap by itself changes nothing on your bill. A DRRS cost could reach an existing fixed price only if the PUCT designated DRRS under 25.475(b)(5) or changed the rule, and then allowed a variation for existing contracts. One of the options Staff put on the table would remove that path entirely. The mid-2028 date is also an estimate, and it can move.

The protection on the other three causes is the same for every term length. For when to lock in, the forward price curve guide covers timing, and the renewal guide covers the notice and switching windows at the end of a term.

How do you check what your own fixed-rate contract allows?

Your Electricity Facts Label (EFL) and Terms of Service spell out exactly when your price can move. Start with the EFL Disclosure Chart's answer to "Can my price change during the contract period?" and the row beneath it, then find the fixed rate section of the Terms of Service.

1. Open your EFL and find the Disclosure Chart. On a fixed rate plan, the row "If my price can change, how will it change and by how much?" should list the same causes as the rule. How to Read Your Texas Electricity Facts Label walks through the rest of the label.
2. Open your Terms of Service and find the pricing language for fixed rate products.
3. Compare the TDU delivery lines on your bill with the current TDU rates for your territory.
4. Follow Project 59997 on the PUCT Interchange, where the PUCT also offers a Filing Notification System.

Ambit Energy's own documents use the rule's three causes. The Ambit Texas Residential Terms of Service (version v. TOU103123, dated October 31, 2023) says: "The price of a fixed rate product may change during a contract term only to reflect changes in TDU charges, changes to the Electric Reliability Council of Texas (ERCOT) or Texas Regional Entity administrative fees charged to loads or changes resulting from federal, state or local laws that impose new or modified fees or costs on REPs, including Ambit Energy, that are beyond our control." To see how Ambit's plans and terms compare, see Every Ambit Energy Plan Compared.

Frequently asked questions

Will DRRS raise my electric bill?

Not on an existing fixed-rate contract under today's rule. A DRRS cost could reach a fixed price only if the PUCT expressly designated DRRS or changed the rule, and neither has happened. ERCOT estimates DRRS will be fully implemented in mid-2028, and no DRRS cost per kWh has been published.

Can a heat wave or an ERCOT price spike raise my fixed rate?

No. Wholesale price swings are not one of the three causes in 25.475(b)(5). A heat wave or a winter storm can raise your bill through higher usage, but not your fixed price. What a Texas winter storm can and can't do to your electric bill covers the winter side.

Is a fixed rate the same as a fixed bill?

No. A fixed rate holds your price, while your bill still moves with the kilowatt-hours you use. Budget billing smooths the bill amount instead, without changing what you pay over the year, as the Average Monthly Billing guide explains.

Does my provider have to warn me before a TDU-driven price change?

It depends on your Terms of Service. Ambit Energy's Texas Residential Terms of Service says: "Price changes resulting from these scenarios do not require us to provide you with advance notice."

Can I weigh in on Project 59997?

Comments go to Project No. 59997 by December 4, 2026, with reply comments by December 18, 2026, according to the Staff memo. Every filing is posted on the PUCT Interchange listing for Project 59997.

Plan details and rates subject to change. TDU charges and ERCOT fees in this article are as of the dates shown.