One word, two meanings
Curtailment, explained
The word means two different things depending on who is doing it. The grid curtails generators, telling wind and solar to back down when the lines are full. Customers curtail themselves, deliberately cutting load when the hours are expensive. In Texas, the second kind is worth real money.
Generation curtailment
When West Texas wind and solar can produce more than the transmission lines can carry, ERCOT turns some of it down. Congestion is the usual reason, and negative overnight prices do the same job through the market. It happens more every year as renewables outbuild the wires. Either way, the grid decides, not you.
Load curtailment
A factory pre-cooling and idling a line for three hours on a July afternoon. A bitcoin mine powering down as reserves tighten. A district cooling plant shifting to ice storage. This one is your decision, and if those hours contain a coincident peak, it pays for itself for a year. The details are on the 4CP page.
The economics, briefly
Curtailment costs you production, comfort, or compute, so the question is always whether the hours you cut were the hours that mattered. Curtail every hot afternoon and you catch every peak while burning out your ops team, 25 or more interruptions a summer. Curtail too little and one missed 15-minute interval costs more than the summer of discipline saved. The math only works with a forecast you can grade: fewer flags, tight windows instead of blanket afternoons, and receipts when it's wrong. Run your own numbers in the savings calculator.
What does curtailment mean?
Reducing electricity output or consumption on purpose. When the grid curtails, it tells wind and solar plants to produce less than they could, usually because of congestion or oversupply. When a customer curtails, a facility deliberately cuts its own demand for a stretch of hours to dodge a coincident peak, respond to prices, or help during an emergency.
What's the difference between curtailment, peak shaving, and load shedding?
Load curtailment is the deliberate, planned reduction of a facility's demand. Peak shaving is the same idea framed around a bill: shaving your highest demand intervals to cut demand charges. Load shedding is the involuntary version, where the grid operator drops customers to protect the system, as Texas saw in the February 2021 winter storm.
Why do wind and solar get curtailed in Texas?
Mostly transmission congestion: West Texas can generate more wind and solar than the lines can carry east to the cities, so the surplus is turned down. Negative prices in windy overnight hours have the same effect through the market.
What is a curtailment worth for a 4CP facility?
Transmission charges in ERCOT are allocated by your load during the four summer coincident peaks. A facility that curtails through the right 15-minute intervals, four a summer, cuts its transmission bill for the entire following year. For large loads that's routinely six or seven figures.
How many times a summer should I expect to curtail?
That depends entirely on how good your peak forecast is. Curtailing every hot afternoon means 25 or more interruptions a summer. Across four graded summers, our calls caught 15 of the 16 monthly peaks with about 20 flagged days a summer. The full record, including the miss, is public.
Four sends a day, max. Free.