GrünstromIndex vs PVWatts

GrünstromIndex (GSI) forecasts, by German postal code, what share of the electricity grid is renewable for the coming hours, so consumers and devices can shift usage toward greener periods. The public front end at gruenstromindex.de is now branded Corrently, and the underlying forecast gateway (api.corrently.io) is HTTPS-only even though the demo site itself still serves over plain HTTP.

PVWatts estimates the energy production and cost of grid-connected photovoltaic systems anywhere in the world, given basic system specs like capacity, tilt, and array type. The National Renewable Energy Laboratory's developer portal was renamed to the National Laboratory of the Rockies (NLR) and its host retired on 2026-05-29 — the API itself is unchanged, just served from developer.nlr.gov instead of the old developer.nrel.gov, which no longer resolves.