Fetch solar irradiance forecasts for a site using the Solcast API
domain: api.solcast.com.au · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Register at solcast.com to obtain an API key; the key is passed as api_key in the query string or as a Bearer token.
For a rooftop or utility-scale site, first create a site in the Solcast portal (or via API) to get a resource_id; alternatively use the live or forecast endpoints with latitude/longitude for unregistered sites (with limitations).
Retrieve a 7-day solar forecast via GET https://api.solcast.com.au/rooftop_sites/<RESOURCE_ID>/forecasts?format=json&api_key=<API_KEY>; the response contains forecasts array with period_end, pv_estimate, pv_estimate10, pv_estimate90, and irradiance fields.
For actual (estimated actuals) data to compare against production, call the estimated_actuals endpoint with the same resource_id to get hindcast values.
Integrate the forecast into dispatch or scheduling logic using the pv_estimate (P50) for expected production and pv_estimate10/pv_estimate90 for uncertainty bounds.
Known gotchas
API call quotas are strict and tied to the number of registered sites and calls per day; each forecast or estimated_actuals call consumes quota — caching results and reusing forecasts within their valid window rather than re-fetching on every application request is essential.
Forecasts are returned in UTC; the period_end field marks the end of each 30-minute period — consuming applications that use period_end as the representative timestamp instead of the period midpoint will misalign forecasts with production actuals by 15 minutes.
Solcast's rooftop model uses system capacity, tilt, azimuth, and loss parameters set at site creation; using default parameters when the actual system is significantly tilted or shaded will produce systematically biased forecasts — configure site parameters accurately.
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