Spanish market data lives behind indicator numbers

Spain publishes generously, but through an API whose entire structure is a catalogue of numbered indicators. Once you know which number you want, everything is easy. Finding the number is the work.

Who is who in the Spanish market

Red Eléctrica (REE) is the transmission system operator and runs ESIOS, the data system. OMIE is the market operator for the Iberian day-ahead and intraday markets, covering Spain and Portugal together as MIBEL.

Almost everything operational comes from Red Eléctrica; prices and matched volumes come from OMIE.

The same guide in Spanish, with operator names and report titles as they appear in the original documentation: API de ESIOS y datos del mercado eléctrico español.

Two doors from the same operator

Start with apidatos. Move to ESIOS when you hit something it does not carry — which happens as soon as you need balancing or settlement detail.

Getting an ESIOS token

Access is free but manual: you e-mail consultasios@ree.es asking for a personal token, and it arrives by reply. There is no self-service signup. The token goes in a header, not a query parameter.

GET https://api.esios.ree.es/indicators/600
    ?start_date=2026-09-15T00:00&end_date=2026-09-16T00:00
Accept: application/json; application/vnd.esios-api-v1+json
x-api-key: {TOKEN}

The Iberian peculiarities

MIBEL is two countries

Spain and Portugal form a coupled market, MIBEL, operated by OMIE. Prices are usually identical across the border and diverge only when the interconnection is constrained. If you model Spain alone and ignore Portugal, most of the time you are right — and the times you are wrong are exactly the interesting ones.

Technical restrictions

After the day-ahead market clears, REE runs a restrictions process that redispatches units for grid reasons, and the result changes who actually generates. Market-clearing schedules and final programmes differ, and both are published. Use the final programme (P48) when you want what happened; use the market result when you want what cleared.

Solar dominates the shape

The Spanish duck curve is the deepest in Europe. Midday prices reach zero or negative regularly, and the evening ramp is steep. Any model trained on northern European shapes will be wrong here in both directions.

Practical notes

• Times are local Madrid time by default; the API accepts a time_trunc parameter and returns a geo breakdown you usually do not want — filter to peninsular Spain unless you deliberately need the islands.
• The Canary and Balearic islands are separate systems with their own prices and no connection to the peninsular market. Mixing them into a national average produces nonsense.
• OMIE publishes as fixed-width and semicolon files, one per day, with Spanish column headers that have been stable for years — easy to parse, tedious to discover.
• Spain also publishes to ENTSO-E under 10YES-REE------0; see our ENTSO-E API guide if you want it in the same shape as other zones.

Frequently asked questions