New England · ISO-NE
The capacity tag
One summer hour sets your capacity bill for a full year. Your facility's demand during the ISO-NE annual peak becomes its capacity tag, and every megawatt you shed during that hour keeps paying until the next one.
What is a capacity tag?
Your facility's average demand during the single hour of the year when New England's total load peaks. ISO-NE allocates capacity costs by that one reading: whatever you were drawing during the peak hour becomes your tag for the entire next capability year, June through May.
When does the peak hour happen?
A hot summer weekday afternoon, usually between 4 and 7 PM Eastern, in June through September. It is unknowable until the season closes, which is why predicting it matters: curtail during the right hour and your tag shrinks for a full year.
How much is it worth?
Capacity charges in New England routinely run into six figures a year for large commercial and industrial facilities. A megawatt shed during the single peak hour keeps paying for twelve months. The exact rate depends on your capacity zone and supplier contract.
How is this different from a transmission tag?
ISO-NE also bills regional transmission on your demand at each MONTHLY peak, so there are twelve more hours worth watching. The annual capacity tag is the big one; the monthly RNS peaks are the fast follow.
How do I catch the peak hour?
Watch the season leader and act when a hotter day threatens it. WattMarkets tracks New England's season peak standing live and publishes a daily call on whether today can take the slot, graded in public like every market we cover.