Book-and-claim electricity procurement (accounting-based electricity supply) · Glossary

With accounting-based electricity supply, a specific quantity of electricity or a generation attribute, such as renewable origin, is allocated to a consumer in accounting terms. For this, the electricity does not have to flow physically from the named plant to that consumer. What is meant is thus an allocation made through bookkeeping, contracts and rules within the electricity system. The term says nothing about which electrons arrive at a particular socket. The physical electricity flow is a separate level.

The reference quantity is an amount of energy, usually in kilowatt hours (kWh) or megawatt hours (MWh). An example: a company consumes 10,000 MWh per year. Through supply contracts, guarantees of origin or a power purchase agreement, it determines which generation this quantity is attributed to. This must be distinguished from power in kilowatts or megawatts. Power indicates how much energy is fed in or drawn per unit of time at a given moment. For accounting, what counts is the amount of energy in a defined period. For grid operation and security of supply, the point in time, the location and the load profile also matter.

Accounting-based allocation and physical electricity flow

In the power grid, no path can be traced from a power plant to an individual withdrawal point. In the European interconnected grid, feed-in and withdrawal must be almost in balance at all times. Where the electricity flows, however, is determined by physics, that is, line impedances, switching states and the current distribution of load and feed-in, and not by trading relationships. If a household in Hamburg uses a green electricity tariff, it is therefore not supplied directly by a particular wind turbine. The grid can be imagined as a lake: many feed in water, many withdraw it, and the contracts only regulate who may feed in and withdraw how much.

This separation applies not only to renewable energy but to the entire electricity system. Coal-fired electricity, exchange-traded electricity or electricity from an industrial power plant is likewise not physically allocated to individual customers. Markets and settlement therefore work with the balancing group. In Germany, every feed-in and withdrawal point must be assigned to a balancing group. The balancing group manager must ensure that feed-in and withdrawal are balanced in every quarter-hour. The manager also bears the financial responsibility for deviations. These deviations are settled via balancing energy. Balancing energy is thus not a freely selectable alternative to a balanced position, but the financial consequence when the balancing group is not balanced. The transmission system operators keep the grid physically stable, for example with control reserve.

Accounting-based electricity supply therefore translates between the world of contracts and the physics of the grid. Without this translation, supplier switching, forward trading, direct marketing, green electricity tariffs and industrial electricity procurement would be hardly possible to organise.

Guarantees of origin, electricity labelling and green electricity

With renewable electricity, not only a quantity is allocated but also an attribute: renewable origin. In Europe this is done mainly via the guarantee of origin (GO). In Germany, the Federal Environment Agency (UBA) issues it electronically, per megawatt hour generated and supplied to final consumers. There is at most one certificate per megawatt hour. Its main purpose is to prevent double marketing of the green attribute. Important for Germany: GOs exist only for renewable electricity for which no payment under the EEG is claimed, that is, neither a feed-in tariff nor a market premium. Electricity supported under the EEG is shown separately in electricity labelling as “renewable energies, supported under the EEG”. Suppliers can demonstrate through regional certificates whether this share was generated regionally.

The electricity itself and the GO can be traded separately. A supplier can buy electricity on the wholesale market and additionally acquire GOs. If it has the GOs cancelled in the UBA register, it may show the corresponding quantity as renewable in its electricity labelling. In Germany, end consumers cannot cancel GOs themselves. This is done by the supplier delivering green electricity to them. According to the UBA, GOs are valid for 18 months but are freely transferable for only 12 months. After that they can only be cancelled. A green electricity tariff can therefore be correct in accounting terms even if the supplier does not deliver from specific plants at the same time and nearby.

Electricity labelling under § 42 EnWG refers to whole years. Suppliers state the energy source mix of the last or second-to-last year, and from 1 July at the latest the values of the preceding calendar year. They must also state CO2 emissions and radioactive waste, both in comparison with the German average. For green electricity with GOs, they must name the countries in which the underlying electricity was generated. Electricity that cannot be clearly attributed to an energy source is shown with an adjusted ENTSO-E mix for Germany. This is checked annually: suppliers report their data to the Federal Network Agency, and the UBA verifies the renewable share.

This annual accounting is legally and in bookkeeping terms something different from simultaneous matching. With temporal matching, matching renewable generation is demonstrated for every hour or quarter-hour. The more wind and solar power is in the system, the more important this difference becomes. An annual balance does not show whether renewable electricity was actually available in hours with little wind and sun.

Distinction from physical supply, self-supply and PPAs

Accounting-based electricity supply is often confused with physical direct supply. Supply is physical in the narrow sense only if the generation and consumption installations are connected via a direct line or within a customer installation. In that case the public grid is not used, or only to a limited extent. The usual supply via the interconnected grid differs from this.

Self-supply is also something different. Anyone who operates a photovoltaic system on their own roof and uses the electricity directly in the building has measurable self-consumption from close proximity. As soon as surpluses are fed in or residual electricity is drawn from the grid, accounting-based allocations arise again. Settlement then separates self-consumption, feed-in and grid withdrawal.

A power purchase agreement (PPA) can be structured in very different ways. In a physical PPA, the generator delivers electricity quantities to the offtaker or its supplier. In the public grid, this too is as a rule accounting-based, that is, via balancing groups, and not via an exclusive line path. In a financial PPA, mainly a price is hedged, and the GOs are transferred separately. Anyone assessing a PPA should check what has been agreed on quantity, profile (for example pay-as-produced or baseload), term, price, transfer of the GOs and balancing group responsibility.

Significance for companies and consumers

Accounting-based electricity supply also plays a role in carbon accounting. Under the Greenhouse Gas Protocol's Scope 2 Guidance, companies report their emissions from purchased electricity in two ways. The market-based method relies on contractual instruments such as supply contracts, PPAs and GOs. These must meet quality criteria intended to rule out double counting between end customers. The location-based method, by contrast, uses the average emission factor of the grid. It can essentially be reduced only by consuming less electricity. The market-based view thus shows procurement decisions, the location-based view the mix to which consumption in the grid area is exposed.

Blanket judgements are misleading in both directions. Accounting-based green electricity is not physically the same as an exclusive supply from wind or solar plants. Nor is the allocation worthless merely because the electricity mixes in the grid. Its value lies in clearly linking demand, payment and generation attribute and preventing double counting. Whether additional renewable plants are built as a result depends on the individual contract. Cheap GOs from depreciated existing plants bring about little additional expansion. With long-term PPAs with new plants, fixed volume commitments and robust financing, the connection with expansion is by contrast usually much stronger.

Time, location and system impact

The more heating, transport and industry are electrified, the more important the timing of electricity consumption becomes. Heat pumps, electric vehicles or electrolysers can be supplied entirely with green electricity in accounting terms. Their effect on the system, however, differs greatly depending on whether they run mainly in hours with surplus or create additional peak load. For flexibility, storage needs and residual load, the time profile counts.

Location also plays a role. A GO from another European country may be admissible for electricity labelling, but the country of origin must then be stated. Grid bottlenecks, the regional generation structure and local loads do not change as a result. Whether a grid section has to be expanded or redispatch costs arise can hardly be answered with such allocations. Grid physics, market accounting and emissions accounting work with different system boundaries.

Accounting-based electricity supply is thus a real and necessary allocation rule, but not a physical supply chain. It shows which quantities and attributes are contractually attributed to a consumer. It does not explain, however, when the electricity was generated, where the grid is loaded and whether additional plants are built as a result. A statement becomes unambiguous only when quantity, period, guarantee of origin, supply contract, balancing group and the desired level of statement are considered together.

Sources

§ 42 EnWG – Stromkennzeichnung, Transparenz der Stromrechnungen, Verordnungsermächtigung — Bundesministerium der Justiz / Bundesamt für Justiz (gesetze-im-internet.de); unbekannt (abgerufen am 11.11.2026). § 42 Abs. 1–5 und 7 EnWG
Fragen und Antworten zu Herkunftsnachweisregister, Regionalnachweisregister, Ökostrom und Stromkennzeichnung — Umweltbundesamt; unbekannt. Abschnitt 2.2 Herkunftsnachweis und FAQ zum Verfall von HKN
§ 79 EEG – Herkunftsnachweise — lxgesetze (Wiedergabe des Gesetzestexts des EEG); unbekannt. § 79 Abs. 1, 2 und 5 EEG
§ 4 StromNZV – Bilanzkreise — buzer.de (Wiedergabe des Verordnungstexts); unbekannt. § 4 Abs. 1–3 StromNZV
Top Ten Questions about the Scope 2 Guidance — Greenhouse Gas Protocol; unbekannt. Abschnitte zur markt- und standortbasierten Methode sowie zu den Scope 2 Quality Criteria

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Edited by eCMS on 11.11.2026 15:43