Guarantees of Origin · Glossary

Guarantees of Origin, GO for short, are the European instrument used to prove the origin of energy to end customers. The German legal term is certificate of origin (HKN). The Renewable Energy Directive (EU) 2018/2001 (RED) defines it as an electronic document. Its sole purpose is to prove to an end customer that a specified share or quantity of energy was generated from renewable sources. In the electricity sector, a GO by default represents one megawatt hour from a specific installation. The English term is customary in trading because the certificates are based on EU law and can be transferred across national borders.

A GO says nothing about the path of individual electrons. It describes an attribute of generation and allocates it, on a book basis, to a supply product or to consumption. One way to picture it is a receipt for green electricity fed into the grid: it can be redeemed only once. But it does not say which electricity actually comes out of the socket.

Content, unit and scope

Under Article 19 RED, a certificate of origin by default covers 1 MWh. At most one certificate may be issued for each unit of energy produced. Since the amendment by RED III, subdivision is possible if the part is a multiple of 1 Wh. At a minimum, the certificate must contain:

the energy source and the start and end dates of generation,
whether it relates to electricity, gas including hydrogen, or heating or cooling,
the name, location, type, capacity and commissioning date of the installation,
whether and which support the installation has received.

GOs therefore exist not only for electricity. Member States may also provide for certificates for energy from non-renewable sources. A GO therefore does not automatically mean renewable energy. What matters is the energy source stated in the certificate. Under EU law, the certificate has no function in determining whether a Member State meets its national renewable energy target. It is an instrument of consumer information.

Validity and cancellation

Under the RED, a GO can be used for consumer information up to twelve months after generation. To prevent the same certificate from being used twice, it is cancelled. It then leaves the tradable stock and is permanently assigned to a specific purpose. More on this under HKN cancellation.

In Germany, the Federal Environment Agency (UBA) operates the register of certificates of origin. Issuance, transfer and cancellation are carried out electronically under the DIN EN 16325 standard. According to the UBA (as of August 2025), an HKN is valid for a maximum of 18 months. However, it can be issued, transferred and cancelled only for twelve months from the month of generation. After that, the register administration declares it expired. Issuance generally takes place monthly for a generation period of one month. In Germany, according to the UBA, only energy supply companies may cancel HKN, and only for electricity labelling. The electricity must have been supplied in the same year in which it was generated. An industrial company in Germany therefore does not cancel certificates itself, but does so via its supplier. In other countries, the rules may differ.

The UBA recognises foreign certificates upon application if they meet the European minimum requirements. Certificates are transferred between the European registers via standardised procedures. Under Section 79 EEG, certificates of origin are expressly not financial instruments within the meaning of German banking law and securities trading law.

Relationship to support schemes

A certificate of origin is not itself a support instrument, that is, neither a feed-in tariff nor a market premium. However, the two are connected. Where a producer receives support, Member States must take the market value of the GO into account. To do so, they may, for example, not issue certificates to supported installations or cancel the certificates immediately. Germany has opted for exclusion: under Section 79(1) EEG 2023, the UBA issues HKN only for electricity for which no payment under Section 19 or Section 50 EEG is claimed. This concerns the market premium, the feed-in tariff and the flexibility payments under Section 50. HKN in Germany therefore come from unsupported installations, for example from other direct marketing or from installations after the end of support. For EEG-supported electricity, regional certificates in a separate register exist instead.

Book-and-claim allocation instead of physical delivery

In the grid, feed-in and withdrawal are balanced physically across the interconnected system. No consumer receives separately routable electricity from a specific installation. A GO answers only one question: for a delivered quantity of electricity, was an equal quantity of renewable generation attribute cancelled? It does not answer whether generation and consumption took place at the same time or in the same grid area, whether congestion was relieved, or whether new installations were built.

The time reference is also coarse. Certificates are usually issued monthly and accounted for annually in electricity labelling. A customer can thus have as many certificates cancelled as they consumed in the year, even though part of their consumption occurred during windless night hours. As the share of wind and solar power grows, this difference becomes more important. For integration into the power system, flexibility, storage and the residual load then matter. Approaches such as temporal matching or granular certificates of origin address this. RED III already allows certificates smaller than 1 MWh to be split and time information to be made more precise. How far this has been implemented in the national registers must be checked case by case.

Relevance for green electricity and procurement

Without a register, it would hardly be possible to verify whether several suppliers claim the same renewable generation for themselves. Anyone in Germany who sells a product as green electricity must cancel corresponding HKN for it. The RED emphasises: if the producer has sold the certificate separately, it may no longer disclose the associated electricity as renewable. Companies also use GOs for the market-based calculation of their electricity emissions. The rules under which this is done are set by separate reporting standards, not by the law on certificates of origin.

The price of a GO depends, among other things, on technology, age of the installation, country of origin and demand. With large supply, the price is often low. The purchase then does document a book-and-claim allocation, but hardly finances new installations. A single certificate from an existing installation therefore does not prove additionality, that is, additional generation. A long-term power purchase agreement can include the associated certificates. The RED requires that such certificates can be transferred to the buyer under the contract. Whether a procurement really promotes capacity expansion depends on the contract form, term and risk allocation.

Distinction from other certificates

In North America, Renewable Energy Certificates are widespread, and in many other countries I-REC. The basic idea is the same: document, trade, cancel. However, the legal basis, register quality and recognition differ. Emission allowances in emissions trading are something entirely different. They certify a right to emit CO₂, not the origin of energy.

What the term achieves and what it does not

Guarantees of Origin make the book-and-claim origin of electricity tradable, verifiable and clearly attributable. For electricity labelling, they are indispensable. Anyone who wants to credibly speak of additional capacity expansion needs stricter criteria. Anyone who wants to show that their consumption matches generation needs data with finer time resolution. Anyone who wants to claim a regional effect needs narrower location criteria.

Sources

Richtlinie (EU) 2018/2001 zur Förderung der Nutzung von Energie aus erneuerbaren Quellen, konsolidierte Fassung — Europäische Union, EUR-Lex; 2023-11-20. Art. 2 (Begriff Herkunftsnachweis), Art. 19 Abs. 1, 2, 7
Directive (EU) 2018/2001 on the promotion of the use of energy from renewable sources — Europäische Union, EUR-Lex; 2018-12-11. Art. 19 Abs. 2 und 3; Erwägungsgründe
Erneuerbare-Energien-Gesetz (EEG 2023), § 79 Herkunftsnachweise — Bundesministerium der Justiz / Bundesamt für Justiz; unbekannt (aktuelle Fassung, abgerufen 2026-11-11). § 79 Abs. 1 bis 7
Die Geltungsdauer eines Herkunftsnachweises — Umweltbundesamt; 2025-08-19. S. 1
Das Herkunftsnachweisregister für Strom aus erneuerbaren Energien (HKNR) — Umweltbundesamt; 2019-07-15. Abschnitte Ausstellung sowie Entwertung/Verwendung, Stromkennzeichnung

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Edited by eCMS on 12.11.2026 05:05