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 · CT · 2-hub average- - day-ahead — real-timeWhere the misses landed
by hub and hour · click a hub to re-scope the chart aboveHub 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 717 paired hours since 2026-07-19. Fills in as the record grows.
Wind swings carry SPP's surprises, so the miss can land any hour of the day. When this chart bulges violet, the wind did something the forecast didn't see.
Tomorrow is already priced
the day-ahead betAug 19, as the day-ahead market cleared it. Real time starts grading at midnight.
Today by hub
day-ahead vs real-time averages| Hub | Day-ahead avg | Real-time avg | Spread |
|---|---|---|---|
| North Hub | $40.51 | $111.77 | +$70.65 |
| South Hub | $62.24 | $84.05 | +$17.55 |
Real-time averages cover graded hours only. Full interval detail is on the prices page.
What is the day-ahead market?
SPP clears a day-ahead market every morning, locking an hourly price for every hour of tomorrow. Most SPP load settles against those prices, and the real-time balancing 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 and a negative number means day-ahead carried a premium.
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. SPP adds wind: the largest wind fleet share of any US market, and a wind forecast that misses by a few gigawatts shows up in real time immediately.
Where does this data come from?
SPP's public market files: day-ahead hourly and real-time five-minute prices for the two trading hubs shown here, the same feeds behind the prices page. Real-time prices accrue live as intervals settle.