PVWatts vs UK Carbon Intensity

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.

This is the official carbon intensity forecast and outturn API for Great Britain's electricity grid, published by National Grid ESO, giving live and forecast gCO2/kWh figures nationally and regionally. It's a fully open government data feed with no key required.