Duck Curve Screensaver
The Duck Curve screensaver plots today's live grid demand for Great Britain hour by hour, showing the real solar-driven midday dip and evening ramp utilities call the "duck curve" — key-less, live from the National Grid Carbon Intensity API. It's free, runs in your browser, and ESC exits.
Live preview
Press ESC to leave fullscreen. Settings are saved in your browser only.
How the Duck Curve screensaver works
The saver fetches today's real half-hourly demand and generation-mix data for Great Britain's grid.
The curve plots demand across the day, dipping as solar output peaks at midday and ramping as the sun sets.
An optional overlay shows solar's real share of generation across the same hours.
The line grows through the day as new real readings publish.
How the duck curve got its name
The duck curve got its name from a chart published by the California Independent System Operator (CAISO) in its Fast Facts material. The chart plotted net load, which is demand minus expected output from variable generation such as solar, for a spring day, starting from actual 2012 data and then projecting later years. Midday formed a deep belly as solar grew, and a steep evening climb formed the neck, giving the outline of a duck.
What this chart shows is slightly different: Great Britain's grid, using the Carbon Intensity API. That service is run by NESO, the National Energy System Operator (formerly National Grid ESO), which developed it with Environmental Defense Fund Europe, the University of Oxford's Department of Computer Science and WWF. It provides carbon intensity and a generation mix by fuel type, such as gas, wind, nuclear and solar, at 30-minute resolution. Britain gets far less sun than California, so the solar dip is smaller.
The shape matters because the evening ramp is the hard part for system operators: as solar fades, other plants, storage or imports must increase output quickly just as people return home. CAISO's chart was meant to show that challenge for California, and the same logic applies in any grid with a growing share of solar.
A worked example
Around midday on a sunny day the curve dips as real solar generation peaks, then climbs sharply into the evening as solar fades and demand stays high — the actual duck-shaped curve grid operators watch for.
Settings & tips
- Solar overlay adds the generation-share line alongside demand.
- Accent recolours the demand curve.
- The curve fills in as the real day progresses — mornings show a shorter line.
Frequently asked questions
- Whose grid is this?
- Great Britain's — the National Grid Carbon Intensity API, a free, key-less, official real-time source.
- Why "duck curve"?
- The demand shape — high morning, a midday dip from solar, a steep evening ramp — resembles a duck's silhouette, a well-known term in grid planning.
- Is a key needed?
- No. The API is free and key-less.
- Is it free?
- Yes — free, no download, in your browser.
- Is this the same duck curve as in California?
- The idea is the same, but this chart shows Great Britain's grid, where the solar share is smaller than California's, so the curve has a different shape.
- What is net load?
- CAISO defines it as forecast load minus expected production from variable generation resources such as solar and wind. It represents what other power sources must supply.
- Why is the evening ramp a problem?
- Solar output drops away at sunset while household demand rises, so other generation, storage or imports must increase rapidly.