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Generation mix

Term generation mix electricity generation power system Energy Market renewable energies

The generation mix indicates which energy sources and power plant technologies the electricity generated in a given area and period comes from. This includes, for example, the shares of wind energy, photovoltaics, hydropower, biomass, lignite, hard coal, natural gas, oil or nuclear energy in total electricity generation. The term is more than a statistical breakdown by energy source. It also says something about the technical characteristics of generation, about costs, emissions, availability and controllability, and about how a power system has to be operated.

The generation mix is usually measured as an amount of energy, that is, in kilowatt hours (kWh), megawatt hours (MWh) or terawatt hours (TWh). One terawatt hour equals one billion kilowatt hours. The shares are often also given in percent. A statement such as "wind energy had a 30 percent share" is therefore unambiguous only with three additional pieces of information: it needs a period, an area and a reference base. An annual value describes something different from an hourly value, and a national value something different from the mix in a grid region.

Energy, power and point in time

The generation mix generally refers to quantities of electricity generated and not to installed capacity. This distinction is central. A country can have a great deal of photovoltaic capacity installed without solar power supplying a large share in every hour. At night photovoltaics generate nothing, no matter how large the installed capacity is. Conversely, a gas-fired power plant with few operating hours can be important for supply in certain situations even though its share of annual electricity volume remains small.

The amount of energy generated results from capacity, operating time and utilisation. An illustrative image: installed capacity is the size of the tap, and the amount of energy is the water that ends up in the bucket. For wind and solar plants the amount depends strongly on the weather. For thermal power plants, fuel availability, technical readiness, maintenance, fuel and CO₂ prices and legal requirements play a larger role. The generation mix is therefore not a simple image of the power plant fleet. It arises from the interplay of technology, weather, prices, grid bottlenecks and market rules.

The point in time also changes what a share means. A kilowatt hour of solar power at a sunny midday affects the system differently from a kilowatt hour from a controllable power plant on a windless winter evening. In the annual statistics both count the same. For grid operation, market price and security of supply they are not equivalent. The German data show how strongly the mix fluctuates over the year: in the third quarter of 2025, according to Destatis, 64.1 percent of domestically produced electricity came from renewable sources. For the full year it was only 58.6 percent. The generation mix is therefore often considered together with the residual load, that is, the load that remains after deducting weather-dependent feed-in.

Reference bases: gross, net and grid feed-in

Gross electricity generation comprises all electricity generated in the plants, including the plants' own consumption. Net electricity generation is the amount after deducting this power plant self-consumption. However, not all net electricity flows into the public grid. Electricity from industrial power plants that is consumed directly on site, or solar power that a household uses itself, is part of generation but is not fed in. Grid feed-in and net electricity generation are therefore not the same thing.

How strongly the reference base influences the result is shown by the year 2025 in Germany. According to the table of the Arbeitsgemeinschaft Energiebilanzen (Working Group on Energy Balances) published by Destatis, gross electricity generation amounted to around 509.8 billion kWh. The share of renewable energies there was 57.2 percent, natural gas 17.1 percent, lignite 14.5 percent and hard coal 5.8 percent. The Destatis monthly survey, by contrast, covers only electricity generated domestically and fed into the public supply grid. For the same period it arrives at 438.2 billion kWh, a renewable share of 58.6 percent, wind power at 30.0 percent, photovoltaics at 16.0 percent and natural gas at 16.1 percent. Both sets of values are correct; they simply measure different things. Some of the values for 2025 are still provisional. Nuclear energy has contributed nothing in Germany since 2024. In 2023 it was still 1.4 percent of gross electricity generation.

Distinction from electricity mix, consumption mix and electricity labelling

In everyday use, generation mix and electricity mix are often equated. This is unproblematic as long as the reference base is clear. The generation mix describes generation within an area. A consumption mix, by contrast, describes which electricity is attributed to consumption in an accounting sense. In interconnected European electricity markets the two diverge, because electricity is traded and transported across borders. According to Destatis, Germany imported around 79.6 billion kWh and exported 60.2 billion kWh in 2025. The import surplus was thus 19.4 billion kWh. The foreign trade statistics record physical quantities at the border crossing points. They do not reveal which energy sources were used abroad to generate the imported electricity.

The electricity labelling for end customers is also not the physical generation mix. In Germany, section 42 of the Energy Industry Act (EnWG) obliges electricity suppliers to state the share of energy sources in their total energy source mix in invoices, advertising material and on their website. In addition there are details on CO₂ emissions and radioactive waste. The labelling refers to the mix the supplier used in the last or second-to-last year. From 1 July of a year at the latest, the previous year's values must be stated. Electricity may be declared as renewable without EEG support only if cancelled guarantees of origin are available for it. These certificates allocate electricity quantities in an accounting sense. They do not change which power plants actually feed in during a particular hour, and they do not replace an analysis of actual power plant dispatch.

Why the generation mix matters for the power system

The generation mix influences how electricity prices arise, what emissions electricity generation causes and what requirements arise for grids, storage and flexible consumers. On the electricity market, power plants are dispatched according to the merit order, that is, by increasing short-run marginal costs. Wind and solar plants have very low variable costs because they need no fuel. Coal and gas power plants, by contrast, depend strongly on fuel and CO₂ prices. The more renewable generation there is, the more the dispatch order shifts, and the price profile over the day often changes as well.

The generation mix is likewise central to the climate balance. The direct CO₂ emissions of a kilowatt hour depend on which power plants are actually running. Wind, solar, hydropower and nuclear energy cause practically no direct CO₂ emissions in operation. Coal and gas do, although gas-fired power plants generally emit significantly less CO₂ per kilowatt hour than coal-fired plants. Average values from the mix do not answer every question, however. If one wants to know how additional consumption affects emissions, what matters more is marginal generation, that is, the plants that respond to an additional kilowatt hour of demand.

The mix also determines how much flexibility the system needs. With high shares of weather-dependent generation, generation and consumption have to be better matched in time. Controllable power plants, storage, load shifting, grid expansion and European electricity trading serve this purpose. In some situations curtailment is added. Renewable plants then feed in less even though wind or sun would be available, for example because of grid bottlenecks, lack of demand or lack of flexibility.

Typical oversimplifications

  • An annual share is not a statement about security of supply: a high renewable share in the annual mix only shows that a lot of renewable electricity was generated over the year. Whether enough firm capacity was available in every hour, including during dark doldrums (Dunkelflauten), power plant outages or peak load, can only be answered by a capacity balance.

  • Share does not equal controllability: wind and sun supply large quantities, but according to weather and time of day. Coal-fired power plants have minimum loads and start-up times. Gas-fired power plants can often be regulated more quickly but incur fuel and CO₂ costs. Hydropower can be very flexible if there are reservoirs or sufficient inflows. How strongly inflows fluctuate is shown by 2025: according to Destatis, feed-in from hydropower fell by 22.5 percent. Biomass is renewable but limited by available fuel quantities, land and sustainability criteria.

  • Imports and exports are neither a seal of quality nor a warning sign: exports often arise from price differences or the grid situation and do not automatically mean lasting surpluses. Imports do not automatically indicate a supply weakness, because cross-border trade is part of normal market activity in the European interconnection and can lower costs. One must, however, disclose whether generation, consumption or quantities allocated in an accounting sense are being considered.

  • Different statistics are not automatically contradictory: values for gross or net generation, for grid feed-in or for the share of gross electricity consumption differ systematically. Comparisons make sense only within the same reference base.

Connection with electrification and system costs

With the electrification of heat, transport and industry, the generation mix becomes even more important. Heat pumps, electric cars and electrolysers increase electricity demand but replace fossil energy sources in other sectors. More electricity consumption therefore does not necessarily mean higher total energy consumption, because electrical applications are often more efficient than combustion technology. How much the climate benefits, however, depends on how the additional electricity is generated and how flexibly the new consumers can be operated.

For costs, looking at the pure generation costs of individual technologies is not enough. A generation mix also causes costs for grids, reserves, ancillary services, storage and, where applicable, for curtailment and redispatch. Redispatch means that grid operators intervene in power plant dispatch in order to manage grid bottlenecks. An inexpensive power plant at a location that is unfavourable for the grid can thus trigger additional costs in the overall system. Conversely, flexible demand at the right location can relieve grids and ensure that more renewable electricity is used.

The generation mix shows which technologies actually supply electricity and which characteristics they bring into the supply system. On its own, however, it does not explain whether a power system works reliably, cost-effectively and in a climate-compatible way. For that, timing, location, controllability, grid capacity, market rules and consumption structure must also be considered. Anyone who cites figures on the generation mix should therefore always state the area, period, reference base and data status as well.

Sources

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Edited by eCMS on 11.11.2026 19:47

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