About this project

You pick your region and an appliance. The site tells you the cleanest time in the next two days to run it — the window when the GB electricity grid is forecast to be lowest-carbon for long enough to finish the load.

Carbon intensity forecasts are published by the National Energy System Operator (NESO) Carbon Intensity API, free and open under CC BY 4.0. The data is half-hourly, regional (14 GB grid regions defined by distribution network operator boundaries), and looks roughly two days ahead. It is a forecast, not a measurement, and the regional feed is flagged beta by the source.

Every half-hour slot in the forecast gets a carbon intensity in gCO₂/kWh. For the appliance's run length, every possible consecutive window of slots is scored by its average intensity, and the lowest-scoring window wins. Ties go to the earliest window — same carbon, sooner is better. When the cleanest and dirtiest windows are within 5 gCO₂/kWh of each other, the site says so and tells you it barely matters, instead of inventing a recommendation.

• No prices, tariffs, bills, or savings in pounds — carbon only.
• No supplier names, switching, or comparison.
• No accounts, no saved preferences, no notifications.
• No chart in this version — one answer, one screen.
• Northern Ireland — it isn't covered by this data source.

You enter a postcode outward code only (the part before the space, like LE1). It is sent to the public Carbon Intensity API to pick a region, and nowhere else. It is never stored, logged, or associated with you — there are no accounts and no database. The data source itself refuses full postcodes, so this is enforced upstream as well as by us.

All timestamps are processed in UTC and shown in UK wall-clock time (BST or GMT, whichever is in effect). Getting this wrong would make every recommendation an hour off for seven months of the year, so conversion happens in exactly one place, at the point of display.