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National Grid ESO vs UK Carbon Intensity

Same instrument, two spec sheets — measured, not claimed.

APINational Grid ESONEW—UK Carbon IntensityNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearyes
Data licenseNESO Open Data Licence (OGL-based); varies per datasetCC BY 4.0 (per API docs)
Free tierFree — limits not publishedFree — no API key
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

National Grid ESO vs UK Carbon Intensity: common questions

Which is more reliable, National Grid ESO or UK Carbon Intensity?

On our scheduled checks, UK Carbon Intensity leads on measured uptime — National Grid ESO at —% versus UK Carbon Intensity at —% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Do National Grid ESO and UK Carbon Intensity need an API key?

Neither needs a paid key — National Grid ESO is callable with no signup, and UK Carbon Intensity is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call National Grid ESO and UK Carbon Intensity from the browser?

Yes — both National Grid ESO and UK Carbon Intensity send CORS headers over HTTPS, so front-end code can fetch either directly with no backend proxy. That makes them easy to swap in a client-side app while you compare responses.

Are National Grid ESO and UK Carbon Intensity free for commercial use?

National Grid ESO has unclear commercial terms, and UK Carbon Intensity allows commercial use on its free tier. We track service terms and the data license as separate fields — see the Commercial use and Data license rows above, and confirm both before shipping either in a paid product.