Day-ahead vs. real-time
Every morning the day-ahead market prices tomorrow, hour by hour. This page grades that bet against what the grid actually paid.
Two prices for every hour
Aug 18 · ET · 11-zone average- - day-ahead — real-timeWhere the misses landed
by zone and hour · click a zone to re-scope the chart aboveZone rows rank by today's average miss. zone mean of the load-zone settlement point prices.
The premium by hour
average spread by hourAverage of 719 paired hours since 2026-07-19. Fills in as the record grows.
The late-afternoon hours that decide the ICAP peak are the hours day-ahead prices hardest. When this chart bulges violet after 2 PM, that is why.
Tomorrow is already priced
the day-ahead betAug 19, as the day-ahead market cleared it. Real time starts grading at midnight.
Today by zone
day-ahead vs real-time averages| Zone | Day-ahead avg | Real-time avg | Spread |
|---|---|---|---|
| CAPITL | $50.87 | $46.76 | −$3.30 |
| CENTRL | $50.07 | $45.62 | −$3.67 |
| DUNWOD | $53.01 | $48.64 | −$3.74 |
| GENESE | $49.28 | $45.55 | −$2.96 |
| HUDVL | $52.24 | $47.75 | −$3.83 |
| LONGIL | $92.99 | $85.10 | −$8.53 |
| MHKVL | $51.54 | $47.36 | −$3.38 |
| MILLWD | $52.71 | $48.31 | −$3.76 |
| NORTH | $49.83 | $45.72 | −$3.29 |
| NYC | $53.60 | $48.85 | −$4.19 |
| WEST | $48.74 | $45.20 | −$2.85 |
Real-time averages cover graded hours only. Full interval detail is on the prices page.
What is the day-ahead market?
NYISO has run a day-ahead market since 1999, the oldest in the country. Bids close at 5 AM and results post by late morning ET, locking an hourly price for every hour of tomorrow. Most New York load settles against those day-ahead prices, and the real-time market trues up the difference every five minutes.
What is DART?
Trader shorthand for the day-ahead to real-time spread. On this page the spread is real time minus day-ahead, so a positive number means the hour settled above its day-ahead price. Virtual traders arbitrage this spread in NYISO too, which tends to keep the averages honest.
Why do the two prices differ?
The day-ahead price embeds a forecast of weather, demand, and which plants will run. Real time is the grid as found. New York adds geography: the constrained path from upstate generation to downstate load means NYC and Long Island carry their own congestion, and their rows on the miss map often diverge from upstate together.
What is an LBMP?
Location-based marginal price, NYISO's name for the zonal price. It bundles the marginal cost of energy with congestion and losses for each of the 11 zones, lettered A in the west to K on Long Island. Both markets on this page settle in LBMPs.
Where does this data come from?
NYISO's public MIS files: day-ahead zonal LBMPs and real-time five-minute zonal LBMPs, the same feeds behind the prices page. On daylight-saving switch days the grid honestly shows 23 or 25 hours.