Four 15-minute intervals set your transmission bill for a year.
ERCOT finds the single highest 15-minute system peak in each of June, July, August, and September. Those four coincident peaks give the 4CP program its name. Your average load during those four intervals is your 4CP. It sets your share of transmission costs for the following year. Be low when the grid peaks and you pay less. Be high and you pay for it monthly, all year.
The dilemma nobody prices in
You can't know a peak is THE peak until the month ends. The blunt answer is to shed load every hot afternoon, June through September. That catches everything and costs you 20 or more interruptions a summer in production, comfort, and credibility with your own ops team. The other failure mode is curtailing four hours at a time when the risk is really a 90-minute window.
Our answer: a calibrated daily probability, a tight window instead of a blanket afternoon, and a public ledger of every call so you can decide how much to trust it. Across four graded summers we flagged 82 days, caught 15 of the 16 peaks, and the hot-day rule needed 105 flags to do the same. The miss is on the page too.
Go deeper
- 4CP dates · every settled peak since 2022 and the live season.
- The live dashboard · the live call and the tight window.
- The track record · every call and how it turned out.
- What is curtailment · what cutting load actually means and pays.
- TDU delivery charges · the bill line 4CP lives inside.
- Methodology · the inputs, the model, the grading rules.
- The glossary · 4CP, 12CP, and every other acronym defined.
- The 12CP transition · what changes if Texas moves to twelve peaks.
What it's worth, in dollars
Your TDSP bills transmission charges on your 4CP demand at filed, public rates. Enter what you could actually curtail and see the number for yourself.
Oncor's filed 4CP charges run $3.40 to $5.48 per kW per month depending on your delivery class. the PUCT rate report has the exact figure for your class. Use the rate on your bill.
That's 5,000 kW times the monthly rate, twelve months running. Catching it means being curtailed during the four peak intervals. Across our graded summers that took about 21 flagged days a summer against 26 for a flag-every-hot-day rule, catching 15 of the 16 peaks.
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