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 30 · PT · 3-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 719 paired hours since 2026-07-31. Fills in as the record grows.
The evening ramp carries the day's scarcity, so those are the hours day-ahead prices hardest. When this chart bulges violet after sunset, that is why.
Tomorrow is already priced
the day-ahead betAug 31, 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 |
|---|---|---|---|
| Northern California | $42.30 | $36.99 | −$0.62 |
| Southern California | $42.23 | $37.16 | +$0.12 |
| Central California | $41.07 | $36.56 | +$0.65 |
Real-time averages cover graded hours only. Full interval detail is on the prices page.
What is the day-ahead market?
CAISO clears a day-ahead market every morning: results post by early afternoon Pacific, locking an hourly price for every hour of tomorrow. Most CAISO load settles against those 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 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. California adds the evening ramp: when the sun sets and demand holds, real time can spike into a ramp that day-ahead only guessed at.
Where does this data come from?
CAISO's public OASIS feeds: day-ahead hourly and real-time five-minute prices for the three trading hubs shown here, the same feeds behind the prices page. CAISO runs on Pacific time and honors 23- or 25-hour days at the daylight-saving switch.