Best European Energy Data APIs (2027): Rated, with AI-Use Licences and Revisions

What is different from the 2026 edition

The 2026 edition (last reviewed 24 Sep 2026) stays online as published, with its integration notes and list prices as of that date. This edition changes the following.

• A licence column for AI use. Taken from our reading of each source's own terms on 20 Oct 2026. The JAO, Euronext, EPEX and EEX texts behind the 2027 section were read again on 29 Oct 2026. It is a reading of terms, not legal advice.
• A revisions column. For GIE AGSI+, GIE ALSI and ENTSO-E imbalance prices it gives counts of corrections from our own capture, published with the method and the change records. For everything else it says “not measured”.
• Nine sources added. NESO, NVE, Gassco, National Gas, SMARD, RTE, JAO, Nord Pool REMIT UMM and netztransparenz.de join the table for their licence and revisions answers. They have no score yet; we score them at the January review.
• SMARD prices, corrected. The 2026 edition said SMARD publishes DE-LU and NL day-ahead prices under CC BY 4.0. SMARD's own manual names the exchanges as the primary owners of wholesale prices, so treat them as needing the exchange's permission.
• FRED and Open-Meteo's free tier move to “not without permission”. FRED's terms bar storing or caching its data and using its API in connection with AI development or training, so we no longer suggest it for a free build. Open-Meteo's free API was always non-commercial; a product or an AI feature needs a paid plan.
• Scores unchanged. The scores are those set in June 2026 and re-checked on 24 Sep. The two new columns sit beside the score rather than inside it, so you can weigh them yourself.

Five criteria and two new columns

Each scored source is rated 0 to 10 on the five builder criteria of the 2026 edition. It weights how easy the data is to integrate and run, not how prestigious the brand is.

• Coverage & authority (30%): breadth, and whether the data is primary or official.
• Developer experience (25%): docs, SDKs, formats, auth simplicity.
• Latency & granularity (20%): how fresh and how fine-grained.
• Reliability & limits (15%): uptime, rate limits, redistribution rights.
• Value for money (10%): cost against what you actually get.

The two new columns

• Licence for AI use: may you store the data, republish it, and feed it to an AI model or agent? “Open with credit” means yes to all three if the credit line travels with the data. “Get it in writing” means the terms lean yes but do not say so. “Not without permission” means the terms need the owner's consent or a licence that names the use. “Your contract” means a commercial licence we did not review.
• Revisions: does the publisher change values after first publication? We record every published value each time we fetch it, so a correction shows up as a value that differs from the first one we saw. Where we have counted, the column says so and the section below gives the counts; elsewhere it says “not measured”, which does not mean values never change.

Every source, rated, with licence and revisions

Licence detail: store, republish, feed to an AI model

Read on 20 Oct 2026 from each source's own terms; JAO, Euronext, EPEX and EEX read again on 29 Oct 2026. “Not established” means the terms we read do not settle it.

One rule cuts the other way. CC BY 4.0, NLOD and the open government licences forbid adding terms that restrict the people you pass the data on to, so a product built on them may not forbid its own users from putting that data into AI.

How often values change after first publication

We record every published value of these series each time we fetch them. Between 23 Sep and 28 Oct 2026 we counted how many were changed after we first saw them. Recording for these series began on 23 Sep, so nothing earlier is covered. Each series is re-read only for a limited window, so later corrections go unseen and every count below is a minimum. The method, the limits and the change records are published: the paper (doi:10.5281/zenodo.23749147) and its dataset (doi:10.5281/zenodo.23749094). Both are ours: the author runs Voltstack, and the capture is Voltstack's.

Imbalance prices keep changing after the window. We re-read them for about three days after delivery, so the counts above include only corrections made in those three days. For delivery on 21 Sep, 96 of the 102 corrected Spanish quarter-hours had changed again by 28 Oct, judged against what ENTSO-E publishes today. A repeat request to these APIs returned the corrected value, so keep the first one yourself if you need it later.

The window is five weeks. Do not read it as “always” or “every winter”. Sources: GIE AGSI+ (https://agsi.gie.eu/) and GIE ALSI (https://alsi.gie.eu/), Gas Infrastructure Europe; ENTSO-E Transparency Platform (https://transparency.entsoe.eu/), CC BY 4.0, aggregated and changed by Voltstack.

Six free official sources you may build on

These six are free to read and, except ENTSOG and ENTSO-E's items off the free re-use list, open to store, republish and feed to an AI model as long as the credit line travels with the data. Integration notes from the 24 Sep review (endpoints, keys, rate limits, parsing traps) are in the 2026 edition.

ENTSO-E Transparency Platform: 9.3

The widest free source of European power fundamentals, but in two halves. The items on ENTSO-E's free re-use list (cross-border flows, load forecasts, transfer capacities, redispatch, balancing and imbalance) are CC BY 4.0. Day-ahead prices, actual total load, and generation and outage data are not on the list and need the owner's agreement before you republish them or feed them to a model. Spain's and Austria's imbalance prices, which are on the list, were corrected often in our capture: see the revisions section.

GIE AGSI+ / ALSI: 9.1

The free standard for EU gas storage and LNG terminal data, with a free key and JSON. Open with credit to GIE, AGSI or ALSI, including for AI use. Both series are corrected after first publication, ALSI most of the time, so store each value with the time you saw it if you need to know later what the number said.

Elexon BMRS (Insights): 8.9

The free route to GB power data: half-hourly generation by fuel and the balancing mechanism, keyless, under a licence that allows commercial re-use and AI use with the Elexon attribution line. Leave out the Market Index (MID) series, which come from the exchanges and carry their rights.

ENTSOG Transparency: 8.6

The free, keyless source for European gas pipeline flows. Its terms allow download, storage and use and set a citation format, but grant no express right to redistribute, so get that in writing before you serve it to others or to their models.

NESO Data Portal: not yet scored

Great Britain's system operator data, including demand and wind forecasts, under the NESO Open Data Licence v1.0. Open with the credit “Supported by National Energy SO Open Data”.

NVE reservoir statistics: not yet scored

Norway's weekly hydro reservoir filling, under the Norwegian open licence NLOD 2.0. Name NVE, link the licence and the service, and mark any changes. Anyone you pass it to holds the same licence from NVE directly.

Paid data, and what the licence lets you do with it

Free official data tells you what happened and what is flowing now. You pay for forward forecasts, vessel and asset-level flows, settlement-grade price assessments and exchange prices. The licence matters as much as the data: on the exchanges' current terms, a licence to display or use prices internally does not by itself let you feed them to a model or show model output to clients.

• Energy Quantified (8.6): the most builder-friendly commercial API, with REST, a WebSocket feed and a Python SDK.
• Kpler (8.5): LNG cargo and pipeline flow tracking over REST and GraphQL, with a Python SDK.
• ICIS / Platts / Argus (8.5): price assessments for OTC settlement, all behind entitlements.
• LSEG Workspace (8.5) and Bloomberg (8.3): terminals for cross-asset coverage and news.
• EEX, ICE and Nord Pool (8.4, 8.1): exchange-direct data on published fees. EEX asks for a separate licence for AI use. Nord Pool's licences say nothing on AI, so get the use in writing.

Before you sign any of these, name the AI use in writing: whether you may put the data into a model or an index, whether the output may reach clients, and whether a vendor's assistant may see it. We did not review these vendors' contracts, which is why the table says “your contract”.

Voltstack, self-assessed: not rated

Voltstack is a browser-based analytics workspace with a read-only data API, built on official European power and gas sources for traders and analysts on European gas and power desks.

What the /v1 API does today

• A read-only JSON API at https://api.voltstack.energy/v1, with GET endpoints for power, gas, weather and history built on sources such as ENTSO-E, GIE, ENTSOG and National Gas.
• The history endpoint takes an as_of time and returns what a series said at that moment, live since 23 Sep 2026.
• Those past values are captured forward only and cannot be back-filled: NESO and RTE forecasts since 31 Jul 2026; ENTSO-E imbalance prices and cross-border flows, GIE AGSI+ and ALSI since 23 Sep 2026; Gassco since 24 Sep 2026; NVE since 21 Oct 2026. Other series are served as currently published.
• Keys go in an X-API-Key header and are issued on request by email to research@voltstack.energy. There is no self-serve key; without one you get a labelled sample.
• Each response names its upstream source. Voltstack grants no right a source does not give, so the licence table above applies to data you reach through it, day-ahead prices included.

Its limits

• It is a secondary source: every value comes from a primary publisher, and it adds no speed of its own.
• In the window the revisions section covers, imbalance prices were re-read for about three days after delivery, so corrections made later were not kept.
• No published price. A 14-day trial covers the app, not an API key.

We do not rate our own product. Voltstack is set against the same criteria and the two new columns in words, with no score and no rank.

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Licence changes builders should plan around

• JAO rewrote its terms in 2026. The current text, undated and in place by 15 Oct 2026, bars making JAO content, including derived outputs, available to any third party without JAO's prior written authorisation (Section A, clause 4), and prohibits training machine-learning models or developing AI in its registered areas without authorisation (Section B, clause 2).
• Euronext treats AI output as redistribution. Its statement of 13 Jul 2026 on its Market Data Agreement and Datafeed Subscriber Agreement counts feeding its data into an AI application as non-display use, and AI output that discloses the data to third parties as redistribution.
• EPEX bars AI use without consent. Its General Conditions of Data Use of 1 Nov 2025 forbid using its information products to train, develop, fine-tune, validate or enhance any AI system, machine-learning model or algorithmic process without prior written consent (clause 3.1.2). EPEX prices that reach you through ENTSO-E or SMARD still need the exchange's agreement (ENTSO-E Terms of Use 3.1; SMARD manual D.3.1).
• EEX makes AI a separate licence. DataSource General Conditions v8, valid from 1 Nov 2025, require anyone using its licensed data within AI solutions to take the appropriate licence (section 3.2.3).
• EEX retired its Transparency API guide. EEX marked its Transparency Data API User Guide (Ref. 8) for decommissioning on 30 Jun 2026, the date it set for retiring the v1 DataSource REST API. By October 2026 the REST API (v2) User Guide had replaced it, with transparency data in its own section, so check code written against the old guide.

Quick answers

Keep both values, with the time each was seen

If a desk keeps only the latest value, it cannot later show what the number said when it acted. If it keeps only the first, it carries figures that were later changed. Voltstack keeps each value it reads with the time it read it, for the series and start dates in the disclosed entry above.

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More European energy reference

Disclaimer: This reference is produced by Voltstack Intelligence for informational purposes only and is not a vendor endorsement or legal advice. Scores reflect Voltstack's builder-centric assessment, set in June 2026 and re-checked on 24 Sep 2026. The licence column is our reading of each source's published terms on 20 Oct 2026, with JAO, Euronext, EPEX and EEX read again on 29 Oct 2026; check the terms yourself before you rely on them. Voltstack appears as a disclosed, self-assessed entry and is not rated or ranked. Voltstack does not accept payment from listed providers. Corrections to research@voltstack.energy.

Sources: the terms of use, licences and data usage pages of ENTSO-E, GIE, ENTSOG, Elexon, NESO, NVE, Gassco, National Gas, SMARD (Bundesnetzagentur), RTE, JAO, netztransparenz.de, Nord Pool, Euronext, EPEX SPOT, EEX, Open-Meteo and FRED, and written replies from Gassco, National Gas and the German TSOs; corrections measured from Voltstack's own capture, 23 Sep to 28 Oct 2026 (doi:10.5281/zenodo.23749147).