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, and 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. Every call is logged when it's made and graded on settled data.