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Groundhog Day API vs National Grid ESO

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

APIGroundhog Day APINEW—National Grid ESONEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedNESO Open Data Licence (OGL-based); varies per dataset
Free tierFree — limits not publishedFree — limits not published
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Groundhog Day API vs National Grid ESO: common questions

Which is more reliable, Groundhog Day API or National Grid ESO?

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

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

Can I call Groundhog Day API and National Grid ESO from the browser?

Yes — both Groundhog Day API and National Grid ESO 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 Groundhog Day API and National Grid ESO free for commercial use?

Groundhog Day API has unclear commercial terms, and National Grid ESO 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.