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How much solar will ERCOT get?
Forecast solar output for the Texas grid plotted against what actually landed — including the evening ramp-down that sets up most of ERCOT's price spikes.
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Forecast solar output for the Texas grid plotted against what actually landed — including the evening ramp-down that sets up most of ERCOT's price spikes.
Solar output peaks at 30,111 MW on Mon 10 AM, against a low of 0 MW — a swing of 30,111 MW across the window. Solar forecast is the heaviest zone at 30,111 MW.
Plotted window Aug 10, 12:00 AM CDT → Aug 11, 12:00 AM CDT. New vintages published hourly; the latest for each hour is shown.
Every line above, and who produced it.
What settled — the realized values every forecast here is scored against.
The grid operator's own published forecast for these hours. Source: ERCOT.
Every settled hour scored against what each forecast said beforehand.
The window peaked at 30,147 MW on Mon 12 PM; ERCOT solar forecast called it 29,198 MW — 949 MW low.
Each day of the window on its own.
Every hour of the window, shaded by load.
| 0 | 6 | 12 | 18 | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mon, 8/10 |
| Series | Peak (MW) | Peak hour | Low (MW) | Average (MW) |
|---|---|---|---|---|
| Solar forecast | 30,111 | Mon 10 AM | 0 | 11,609 |
| Solar settled (recent) | 30,147 | Mon 12 PM | 0 | 12,916 |
| Forecast | Avg miss (MW) | Avg miss % | Bias | Hours |
|---|---|---|---|---|
| ERCOT solar forecast | 452 | — | −297 | 23 |
The latest published vintage of each forecast, against what settled. Smaller is better on every column. Bias is signed: positive means the forecast ran high.
| Forecast | Produced by | Method | Horizon |
|---|---|---|---|
| Solar forecast | ERCOT | Solar Power Production forecast, report NP4-745-CD (COP HSL, STPPF, PVGRPP) | Hourly, forward across the published forecast window |
ERCOT publishes several solar forecast variants as point values, with no confidence band. Cloud cover is the dominant source of error.
ERCOT publishes an hourly solar generation forecast for the Texas Interconnection. This page plots the system-wide forward forecast alongside recent actual output from the same feed, on one axis.
Solar is now the fastest-growing resource on the ERCOT system, and its daily shape creates the grid's sharpest operational moment. Output falls to zero over the couple of hours after sunset while demand is still near its daily peak — so the steepest ramp on the system happens in the early evening. That is when ERCOT prices most often spike, and it is visible directly in the shape of this curve.
Solar forecasts are generally more reliable than wind forecasts because the daily envelope is fixed by the sun. The error is almost entirely cloud cover, which shows up as the actual line falling below a smooth forecast on overcast days.
curl "https://askthegrid.com/api/v1/grid/radar/curves?iso=ERCOT"
Connect your agent to mcp.askthegrid.com and this forecast is a tool call away — the same host Claude and ChatGPT connectors already use.
It is ERCOT's hourly projection of how much electricity the Texas solar fleet will generate, published by region in report NP4-745-CD. ERCOT publishes several variants, including the current-operating-plan high sustained limit and its own short-term photovoltaic power forecast.
Because solar output falls to zero over roughly two hours after sunset while demand is still close to its daily peak. Dispatchable generation and batteries have to cover that gap very quickly, and when the available fleet is tight, prices in those hours can run into the hundreds or thousands of dollars per megawatt-hour.
Utility-scale solar has been the fastest-growing resource in ERCOT since 2023 and now supplies a substantial share of daytime demand, with wind and solar together meeting roughly a third of total electricity in recent years.
More accurate than the wind forecast, because the daily envelope is set by the sun and only the cloud-cover component is uncertain. The largest errors happen on partly cloudy days and during widespread cloud events.
| Tue, 8/11 |
|---|
Darkest cells are the tightest hours. The week peaks at 30,111 MW on Mon 10 AM, and the daily band across the late afternoon and early evening is the solar ramp-down meeting air-conditioning load.
No. These figures are utility-scale solar generation reported to ERCOT. Distributed rooftop solar behind the meter reduces measured demand instead of appearing as generation, so it shows up in the load forecast rather than here.