The three CAISO trading hubs on one axis: what settled in real time and what the day-ahead market cleared — with the spread between north and south, which is the congestion story of the market, visible directly.
What will power cost in California?
CAISO hub prices peaks at $139 on Thu, 1 PM, against a low of $28.08 — a swing of $111 across the window. SP15 is the heaviest area at 293 $/MWh.
Every line above, and who produced it.
The settled real-time price at this hub. Source: CAISO.
The settled real-time price at this hub. Source: CAISO.
The settled real-time price at this hub. Source: CAISO.
Congestion is why these price apart. Each hub’s settled price with every forecast published for it.
Each day of the window on its own.
Every hour of the window, shaded by load.
| 0 | 6 | 12 | 18 | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Thu, 8/27 |
| Hub | Peak ($/MWh) | Peak hour | Low ($/MWh) | Average ($/MWh) |
|---|---|---|---|---|
| SP15 | 293 | Thu, 6 AM | 79 | 118 |
| NP15 | 139 | Thu, 1 PM | 28 | 74 |
| ZP26 | 142 | Thu, 1 PM | 33 | 70 |
| Forecast | Produced by | Method | Horizon |
|---|---|---|---|
| NP15 settled | CAISO | CAISO day-ahead and fifteen-minute real-time LMPs at the trading hubs | Day-ahead clears once daily; real-time settles every fifteen minutes |
| ZP26 settled | CAISO | CAISO day-ahead and fifteen-minute real-time LMPs at the trading hubs | Day-ahead clears once daily; real-time settles every fifteen minutes |
CAISO publishes cleared prices, not probabilistic forecasts, so no band is shown. Real-time prices swing hard around the evening ramp and can go negative in the solar midday — divergence from day-ahead is routine, not exceptional.
This shows the settled real-time price at CAISO's three trading hubs alongside the day-ahead price the market cleared for the same hours. SP15 covers Southern California, NP15 the north, ZP26 the Central Valley corridor between them. The gaps between the three lines are congestion made visible.
California prices live on the duck curve. Midday solar routinely pushes real-time prices to zero or below, and the evening ramp — solar falling away while demand holds — produces the day's highs. The day-ahead market prices that ramp in advance; where real time diverges from it is where batteries and traders make and lose money.
CAISO's day-ahead market is a financially binding auction that clears the day before delivery. Its prices are the market's own collective forecast — carrying risk premia and hedging positions, which is exactly why scoring it against what settled is worth doing.
curl "https://askthegrid.com/api/v1/grid/series?iso=CAISO&metric=dam&node=TH_SP15_GEN-APND"
Connect your agent to mcp.askthegrid.com and this forecast is a tool call away — the same host Claude and ChatGPT connectors already use.
CAISO's three aggregated trading hubs: SP15 covers Southern California, NP15 the north, and ZP26 the Central Valley corridor between them. They are the reference prices California power is bought, sold, and hedged against.
Midday solar can exceed what the grid can absorb, and solar with production incentives keeps generating at prices below zero. Negative midday prices followed by triple-digit evening prices in the same day is the normal shape of the market, not a malfunction.
Day-ahead clears on expectations; real time clears on what happens. Cloud cover, the speed of the evening ramp, and unit outages all move real time away from the day-ahead clearing price — and that spread is what storage dispatch is positioned against.
Plotted window Aug 27, 12:00 AM PDT → Aug 27, 11:45 PM PDT. Real-time updates continuously; day-ahead once per day around midday.
Darkest cells are the tightest hours. The window peaks at 139 $/MWh on Thu, 1 PM, local to the market.