ERCOT Ancillary Services Are About 1 Percent of Wholesale Cost as the 2027 Reserve Rules Head to the PUCT
ERCOT's Board sent its 2027 reserve methodology to the PUCT on September 15, 2026. Ancillary services cost $0.39 per MWh in 2025, about 1 percent of wholesale cost, so for commercial buyers the contract wording matters more than the level.
On September 15, 2026, the ERCOT Board recommended that the Public Utility Commission of Texas (PUCT) approve the 2027 methodology that sets how much reserve capacity ERCOT buys each hour. The cost at stake is small: ERCOT ancillary services averaged $0.39 per MWh of load in 2025, about 1 percent of the $38 per MWh all-in wholesale price, according to the Independent Market Monitor. For Texas commercial electricity buyers, the level matters less than who carries the swing. In 2023, the same cost ran roughly ten times higher.
What Happened
The ERCOT Board voted on September 15, 2026 to recommend the "2027 ERCOT Methodologies for Determining Minimum Ancillary Service Requirements" to the PUCT, which must approve the methodology before it applies. ERCOT expects a PUCT vote in November or December 2026 and an effective date of January 1, 2027. The package leaves the Regulation Up, Regulation Down and Responsive Reserve Service (RRS) methodologies unchanged, so their 2027 quantities roll forward from historical data. RRS keeps its 1,377 MW floor for primary frequency response.
The changes land on two products: ERCOT Contingency Reserve Service (ECRS) and Non-Spinning Reserve Service (Non-Spin). In daytime hours (hour ending 6 through hour ending 22), the headroom credit rises from 25 percent to 50 percent for generation and to 60 percent for energy storage that can sustain four hours of output. The overnight credit stays at 60 percent. The headroom credit is the share of spare capacity, above what resources are already committed to provide, that ERCOT counts toward covering forecast errors and outages. A higher credit means ERCOT calculates that it needs to buy less ECRS and Non-Spin. ERCOT also moved the target its model solves to, from the 3,000 MW Watch level to the 2,500 MW Energy Emergency Alert Level 1 (EEA1) threshold, a shift ERCOT describes as having only a marginal effect.
ERCOT modeled each option at 2025 prices:
| Scenario (ERCOT label) | Daytime headroom credit (generation / 4-hour storage) | Target threshold | Modeled cost at 2025 prices |
|---|---|---|---|
| No headroom credit (S1) | 0 percent | 3,000 MW (Watch) | $244.03 million |
| Higher credit, Watch threshold (S2) | 50 / 60 percent | 3,000 MW (Watch) | $208.97 million |
| ERCOT proposal (S3) | 50 / 60 percent | 2,500 MW (EEA1) | $208.18 million |
| Aggressive alternative (S4) | 100 percent | 1,500 MW | $127.80 million |
Source: ERCOT Board Item 18, September 2026. The overnight credit is 60 percent under the proposal.
The S4 case matters for the PUCT review. In June 2026, Jeff McDonald, Ph.D., the ERCOT Independent Market Monitor director at Potomac Economics, asked ERCOT to model shorter forecast-error horizons, full credit for available capacity and one-hour storage accounting. S4 follows that direction and came in about 39 percent below the proposal. Read the full ERCOT Board Item 18 package, ERCOT's preview and PUCT timeline, and the Independent Market Monitor's overview of its 2025 State of the Market Report.
Impact on Commercial Electricity Buyers in Texas
Ancillary services reach a commercial bill through the retail electric provider, which pays ERCOT based on its customers' share of total load, and the dollar amount is small next to energy and delivery charges. We see three channels that matter for a business signing or renewing a 2027 contract.
Bill share. $0.39 per MWh equals 0.039 cents per kWh. In the commercial plans we track across all five TDU territories (Oncor, CenterPoint, AEP Texas Central, AEP Texas North and TNMP), median plan rates sat between 6.4 and 6.6 cents per kWh as of September 30, 2026, so 2025-level reserve costs work out to roughly 0.6 percent of a typical rate. The gap between ERCOT's proposal and the same credits under the old Watch threshold is $0.79 million across the whole grid, which rounds to nothing on a single account.
Pass-through language. A fixed-rate commercial offer can fold ancillary services into the energy price for the whole term, or it can bill them as a separate line. Some contracts also let the provider adjust the price when ERCOT market rules or fees change. A new PUCT-approved methodology taking effect January 1, 2027 is exactly the kind of change those clauses cover, so the contract wording matters more than the dollar estimate.
Volatility. The level is low today, but it has not been stable:
| Year | Ancillary service cost ($/MWh of load) | All-in wholesale price ($/MWh) | Ancillary share of all-in |
|---|---|---|---|
| 2023 | $3.74 | $70 | about 5 percent |
| 2024 | $0.98 | $34 | about 3 percent |
| 2025 | $0.39 | $38 | about 1 percent |
Source: Potomac Economics, Independent Market Monitor State of the Market reports for 2024 and 2025.
ERCOT launched ECRS on June 10, 2023, and high ECRS prices that summer drove the 2023 spike. Costs then fell 74 percent in 2024 and another 60 percent in 2025 as milder peaks, more supply including battery storage, and smaller purchase quantities pushed reserve prices down. ERCOT also switched to Real-Time Co-optimization plus Batteries (RTC+B) on December 5, 2025, which buys energy and reserves together in real time and prices reserve scarcity through Ancillary Service Demand Curves. In February 2026 the Independent Market Monitor told ERCOT's board that Non-Spin was clearing at shortage prices even when the system held surplus reserves, a sign that pricing under the new design is still settling.
The TxCP Reserve Cost Check: Three Questions Before You Sign a 2027 Rate
Before accepting a 2027 commercial offer, run the reserve line through the same three questions we use when we read an ERCOT market change, so a small cost does not turn into a surprise adjustment in the middle of your term.
1. Is ancillary service cost inside my fixed price?
If the offer bundles reserves into a fixed energy rate for the full term, the provider carries the 2027 methodology risk for the life of the contract. If reserves are billed separately, you carry it.
2. Can the price change if ERCOT rules change?
Look for language on changes in law, market rules, or ERCOT fees and charges. A clause like that can reopen a fixed price when the PUCT approves a new reserve methodology.
3. How many methodology cycles does my term cover?
ERCOT sets the methodology every year. A 36 month contract starting in January 2027 spans the 2027, 2028 and 2029 methodologies, so a pass-through clause carries three rounds of rule changes, not one.
What You Should Do
This recommendation calls for a contract read, not a rushed decision, and these four steps take less than an hour for most commercial accounts.
- Open your current contract and Electricity Facts Label and search for "ancillary," "pass-through," "ERCOT charges" and "change in law."
- Estimate your exposure by multiplying your annual MWh by $0.39 (the 2025 level) and by $3.74 (the 2023 level). A business using 50,000 kWh a month, or 600 MWh a year, lands at $234 a year at 2025 levels and $2,244 at 2023 levels.
- If you are comparing 2027 fixed-rate offers this quarter, ask each provider to confirm in writing whether reserve costs are included for the full term.
- Judge offers on the energy rate, term length and TDU delivery charges first. The PUCT vote in November or December 2026 is not a reason to delay a good offer.
Questions to Ask Your REP or Broker
These questions pin down how a provider handles reserve costs, which rarely shows up on a rate comparison but decides who pays when ERCOT changes the rules.
- Are ERCOT ancillary service charges included in my fixed rate for the entire term?
- If they are billed separately, how is the charge calculated, and what did it average per kWh on comparable accounts in 2025?
- Does the contract allow a price adjustment if the PUCT approves new ERCOT reserve requirements for 2027?
- Would you fix the ancillary service component if I sign a 24 or 36 month term?
We will follow the PUCT decision as it moves. Subscribe to Weekly Market Insights, free. We publish a data-driven rate report every Monday.
For how 2027 price expectations are shaping offers, see our read-through on ERCOT wholesale prices through the July 22 peak. To compare offers for your meter, browse current commercial rates by TDU or see every commercial plan we track in our data download.
Frequently Asked Questions
What are ERCOT ancillary services?
ERCOT ancillary services are five reserve products the grid operator buys to balance supply and demand and recover from sudden outages: Regulation Up, Regulation Down, Responsive Reserve Service (RRS), ERCOT Contingency Reserve Service (ECRS) and Non-Spinning Reserve Service (Non-Spin). Retail providers pay for them based on their customers' share of ERCOT load, and that cost flows into commercial rates.
How much do ancillary services add to a Texas commercial electricity bill?
About 0.039 cents per kWh at 2025 levels. The Independent Market Monitor put 2025 ancillary service costs at $0.39 per MWh of load, roughly $7.80 a month for a business using 20,000 kWh. At the 2023 level of $3.74 per MWh, the same business would have paid about $74.80 a month.
When do the 2027 ERCOT ancillary service rules take effect?
January 1, 2027, if the PUCT approves them. The ERCOT Board recommended the 2027 methodology on September 15, 2026, and ERCOT expects the PUCT to vote in November or December 2026.
Will the 2027 methodology raise or lower ancillary service costs?
ERCOT's modeling points to smaller ECRS and Non-Spin purchases, because a higher daytime headroom credit reduces the quantity ERCOT must buy. ERCOT modeled its proposal at $208.18 million at 2025 prices, against $244.03 million with no headroom credit. Actual 2027 costs will depend on prices, weather and reserve supply.