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National Grid ESO vs Weather Underground API

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

APINational Grid ESONEW—Weather Underground APIREACHABLE—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthnoneapiKey
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseNESO Open Data Licence (OGL-based); varies per datasetUnverified
Free tierFree — limits not publishedFree tier — API key may be required for production
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

National Grid ESO vs Weather Underground API: common questions

Which is more reliable, National Grid ESO or Weather Underground API?

On our scheduled checks, Weather Underground API leads on measured uptime — National Grid ESO at —% versus Weather Underground API 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 Weather Underground API need an API key?

National Grid ESO needs no key, while Weather Underground API requires a free API key. If you want to start calling without signup, reach for National Grid ESO first.

Can I call National Grid ESO and Weather Underground API from the browser?

Yes — both National Grid ESO and Weather Underground API 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 Weather Underground API free for commercial use?

National Grid ESO has unclear commercial terms, and Weather Underground API has unclear commercial terms. 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.