About this site

The grid is getting greener, and renewable power is cheap. That is the official story, told by ministers, regulators and the industry. What it leaves out is reliability: how much of Britain's electricity, at any moment, comes from firm power you can call on whatever the weather — and how much leans on wind, solar and imports that fall away together when a cold, still spell settles over north-west Europe.

The numbers are public. Elexon, NESO and DUKES publish generation, demand and capacity — every few minutes, and every year — but in separate feeds, in industry units, and framed around carbon and cost, not around whether the lights stay on.

Grid Margin reads them for reliability instead: live in your browser, and from the grid's own settled records, half-hour by half-hour. Every figure traces to its source; the full method is on the methodology page. Nothing is modelled — and where a figure carries a known bias, such as the deliberately conservative lower-bound wind capacity factor, it is disclosed on the page, not buried in a footnote.

The grid operator already keeps this account. NESO plans to a margin — the spare firm capacity above demand — and de-rates wind, solar and interconnectors in that sum, because it cannot count on them in a crunch: a cold, still spell becalms north-west Europe all at once, so the neighbours you would import from are short at the same moment. The public conversation rarely does the same arithmetic. This is a citizen's version of that margin, kept in plain sight.

Built and self-funded by Richard Lyon, author of The Energy Trap (Swift Press, 2026), and sibling to the Subsidy Clock — which measures the cost of energy policy as this measures the risk. No advertising, no sponsors. Get in touch.

The underlying data is Elexon's (BMRS), NESO's and DUKES'; the independent solar cross-check is Sheffield Solar's PV_Live. Each is cited where it is used on the methodology page.

If you find an error in a published figure, I want to know: the figures and the code are in the open repository, and confirmed errors are corrected and logged.

Journalists: figures on this site may be quoted with attribution; I'm available for comment.

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