Generation fleet · Glossary

Definition and scope

The generation fleet is the totality of installations that can generate electricity within a defined system boundary. This boundary can be a country, a control area, a market area, a grid area or an individual company. It includes thermal power plants, wind and photovoltaic installations, hydropower and biomass plants, combined heat and power installations and industrial self-generation. Depending on the perspective, storage facilities are also included, provided they feed electricity back into the grid. Emergency power generators are included only in very broad perspectives. Official overviews usually omit them because they mostly do not feed into the public supply grid.

The term is broader than power plant fleet. The power plant fleet often refers to the fleet of large, centrally controlled power plants, such as coal, gas, nuclear, hydropower or biomass plants. Their capacity can be clearly attributed and they are operated according to a technical schedule. The generation fleet, by contrast, reflects the full diversity of a modern electricity system. This includes many small, decentralised and weather-dependent installations whose feed-in cannot be planned as it can for a thermal power plant. In practice, however, the delimitation is not used consistently. Anyone comparing figures should therefore always check which installation classes and which system boundary underlie them.

Installed capacity: an ability, not a guarantee

The most important technical variable is installed capacity. It is stated in kilowatts, megawatts or gigawatts and describes the maximum electrical output of an installation under defined conditions. Statistics usually refer to net rated capacity, that is, the output after deducting the installation's own consumption. For photovoltaics, capacity is often stated as module capacity in kilowatt-peak. This value can differ from the inverter capacity at the grid connection. A photovoltaic installation of 10 megawatts reaches this output only in strong irradiation. A 500-megawatt gas power plant can be operated in a more targeted way, but depends on fuel supply, maintenance, emission requirements, economic viability and grid connection. Installed capacity therefore describes an ability, not a guaranteed feed-in.

An example shows how strongly the figure depends on the system boundary. The Bundesnetzagentur's power plant list shows for Germany, with a data status of 26 June 2026, a total net rated capacity of 294.7 gigawatts. Of this, 279.8 gigawatts are active on the electricity market and 206.5 gigawatts are from renewable energy sources. The remainder is outside the market, for example in the grid reserve or capacity reserve. Installations of 10 megawatts or more per site are listed individually; smaller installations as well as wind and photovoltaic installations are aggregated by energy source and federal state. In addition there are power plants from Denmark, Luxembourg, Austria and Switzerland that feed into the German grid. Small storage units below 13.2 kilowatts and emergency power generators are missing. Since 2021, the data are based on the Marktstammdatenregister (core energy market data register).

Capacity, energy quantity and capacity value

To be distinguished from installed capacity is the quantity of electricity generated, in kilowatt-hours, megawatt-hours or terawatt-hours. A wind farm and a gas power plant with the same capacity can deliver very different quantities over the year. Decisive factors are the full-load hours, the weather, fuel and market prices, technical availability and regulatory requirements. A single gigawatt figure therefore never describes a generation fleet adequately. For security of supply, energy quantity, availability over time and spatial integration all count at once.

A third variable is the capacity value. It indicates what contribution an installation or group of installations can make to covering load in tight hours. For wind and solar, it is often well below installed capacity because these sources are not available on demand. This does not make them worthless for security of supply, but their contribution is calculated differently. Dispatchable power plants do not reach one hundred percent either, since outages, overhauls, fuel shortages and requirements must be factored in. How much firm capacity a fleet offers is therefore a question of probabilities. There is no fixed property of individual technologies that one could rely on. The capacity value also depends on the rest of the system: the more installations of the same type there are, the smaller the additional contribution of each further one usually is.

The generation fleet is often confused with annual generation or with the electricity mix. The electricity mix shows the shares of energy sources in the electricity quantity of a period. The generation fleet describes the installations, that is, the technical possibilities and limits from which this mix arises. A country can have a lot of installed solar capacity and still show only a small solar share in the mix during the winter half-year. Conversely, an installation that runs only a few hours a year can be important for security of supply if it is available in scarcity situations. Annual quantities say how much energy was generated. They do not say whether enough capacity is available on a low-wind winter evening.

Storage in the generation fleet

Storage must be classified carefully. A battery storage system is not an energy source. It takes up electricity, holds it for a limited time and releases it later with losses. At the moment of discharge, it acts like a power plant for the grid, but in the energy balance it depends on prior generation. Pumped storage, batteries and hydrogen chains differ greatly in capacity, energy content, storage duration, efficiency and cost. In hydrogen chains, electricity is converted into hydrogen by electrolysis and later reconverted into electricity in power plants. A battery storage system with high capacity that lasts only two hours contributes less to a multi-day lull than its capacity rating suggests. Storage thus does not create new energy sources. It shifts energy over time and helps to manage scarcity situations. The Bundesnetzagentur's power plant list includes battery storage from 13.2 kilowatts, but not smaller home storage units.

Spatial distribution and grids

Where the installations of a generation fleet are located determines which lines are needed and where bottlenecks arise. In Germany, wind energy is generated mainly in the windy north, while large consumption centres are also in the south and west. Photovoltaics feed to a large extent into distribution grids. These grid levels were originally designed mainly to supply consumers. Grid operators must therefore accept feed-in, maintain voltage, manage bottlenecks and curtail installations when grid capacity is lacking. For congestion management, Germany additionally maintains the grid reserve. These are power plants that wanted to shut down but must remain operational for reasons of system security. A generation fleet is therefore not a mere list of installations, but also a question of grid engineering.

Cost structure, market and reserves

For the electricity market, the cost structure of the fleet shapes price formation. Wind and photovoltaics have very low variable costs. In hours with high feed-in, they displace more expensive power plants from the merit order and lower the exchange price. If many installations of the same type feed in simultaneously, however, this can reduce their own market value. Dispatchable installations then earn less from continuous generation and more in scarcity hours, with flexibility products or in reserves. This gives rise to an investment problem: the system needs certain capabilities, but the energy market mainly remunerates kilowatt-hours generated and short-term scarcity.

In Germany there are several supplements to the electricity market for this purpose. The capacity reserve under § 13e EnWG has been formed outside the electricity markets since the winter half-year 2020/2021. Its installations feed in only at the request of the transmission system operators and may not sell their capacity on the market. In addition, there is the grid reserve under § 13d EnWG. Since 2026, the Bundesnetzagentur has additionally been tendering new dispatchable capacity on the basis of the Stromversorgungs- und Kapazitätengesetz (StromVKG). In the first round for long-term capacities (bid deadline 8 September 2026, awards on 3 November 2026), the tendered volume was 4,500 megawatts of reduced capacity. Eleven bids with around 5,160 megawatts were awarded. The fact that tenders are made in reduced capacity shows that, from a regulatory perspective too, rated capacity alone does not simply count. A second round has been announced; a comprehensive capacity market is politically envisaged.

A fleet in constant change

The generation fleet is not a fixed quantity. Power plants are built, modernised, decommissioned or transferred into reserves. Wind and solar capacity grows in many small projects, and industrial companies change their self-generation. Political decisions, permitting law, fuel and CO₂ prices, interest rates, supply chains and grid connections determine what actually gets built. In Germany, final decommissionings of larger power plants must be notified in advance. The transmission system operators then examine whether the installation is system-relevant and must continue to be operated for the time being. A planned fleet is therefore something different from an available one. Between a political target, an approved project, a constructed installation and capacity available on the market lie several steps.

Electrification, too, can be better understood with this term. If heating, transport and industry use more electricity, electricity demand rises. Total energy consumption does not necessarily rise to the same extent, because electric applications such as heat pumps or electric motors are often more efficient than direct combustion. For the generation fleet, however, electrification means that more capacity must be available at certain times. Heat pumps increase load in cold winter hours. Electromobility can cause load peaks or, with smart control, shift them. Industrial processes need high capacities and reliable schedules. The fleet must therefore be considered together with load profiles, grids and flexibility options.

What the term achieves and where it reaches its limits

Anyone who uses the term precisely can see which capabilities exist in the electricity system and which are lacking. It does not explain security of supply on its own, since grids, demand flexibility, storage, imports, market rules and operational reserves are also decisive. Nor does it explain electricity costs on its own, because financing, regulation, taxes, levies, fuel prices and grid charges are added. But it provides the technical and economic basis on which these questions can be meaningfully posed.

A generation fleet is thus more than a sum of installed megawatts. It is a concrete landscape of installations with its own generation profiles, availabilities, costs, dependencies and grid relationships. Anyone assessing it should ask: What capacity is available when? What energy quantities add up over the year? Which installations are dispatchable, where are they located, and under which market and grid rules are they deployed?

Sources

Kraftwerksliste — Bundesnetzagentur; Datenstand 26.06.2026. Abschnitte „In der Kraftwerksliste sind aufgeführt“, Tabelle „Erzeugungsanlagen“, „Datenquelle“, „Zu- und Rückbau von Kraftwerken“
§ 13e EnWG Kapazitätsreserve — Bundesministerium der Justiz / gesetze-im-internet.de; unbekannt (aktuelle Fassung). § 13e Abs. 1–3 EnWG
StromVKG – Ergebnisse der ersten Ausschreibung für Langzeitkapazitäten — Bundesnetzagentur; 03.11.2026. Pressemitteilung, Abschnitt „Ergebnisse der Ausschreibung“

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Edited by eCMS on 11.11.2026 19:47