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National Grid ESO vs RainViewer

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

APINational Grid ESONEW—RainViewerNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseNESO Open Data Licence (OGL-based); varies per datasetUnverified (attribution requested)
Free tierFree — limits not publishedFree — limits not published
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

National Grid ESO vs RainViewer: common questions

Which is more reliable, National Grid ESO or RainViewer?

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

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

Can I call National Grid ESO and RainViewer from the browser?

Yes — both National Grid ESO and RainViewer 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 RainViewer free for commercial use?

National Grid ESO has unclear commercial terms, and RainViewer 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.