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Generation profile

Term generation profile electricity generation wind energy photovoltaics load profile residual load market value flexibility

A generation profile describes the time pattern of electricity generation of a plant, a technology or a generation fleet. It shows at which points in time what amount of electrical power is generated. Such a profile can be presented in minutes, quarter-hours, hours, days, months or years. For the power system, this time structure is just as important as the annual amount of energy, because generation and consumption must be balanced at every moment.

Which unit is appropriate depends on what is being shown. Power at a given point in time is expressed in kilowatts, megawatts or gigawatts. The amount of energy generated over a period is measured in kilowatt-hours, megawatt-hours or terawatt-hours. A generation profile links both levels. It shows not only how much energy is produced in total, but also the time sequence of power values from which this amount derives. The area under the power curve is the energy generated. Two plants can generate the same number of kilowatt-hours per year and still affect the grid, the market and security of supply very differently if they feed in at different times. Their installed capacity can even be identical.

For wind power and photovoltaics, the profile is determined above all by weather, time of day, season and location. Photovoltaic plants generate only in daylight. A bell-shaped daily curve with a peak around midday and a strong difference between summer and winter is typical. Wind turbines follow wind speed, large-scale weather patterns and regional conditions. Offshore wind, coastal sites and inland sites have different profiles even though they belong to the same technology. In the case of dispatchable generation, by contrast, the profile results from technical capabilities, fuel and emission costs, market prices, availability, schedules and the requirements of grid operation.

Distinction from load profile, feed-in profile and residual load

A generation profile must be distinguished from the load profile, which describes the time pattern of electricity consumption. The generation profile, in contrast, shows generation over time. In the operation of the power system, both profiles must be continuously brought together. However, they describe different sides of the balance.

The term feed-in profile is closely related, and in everyday use both terms are often used interchangeably. A more precise distinction is nevertheless helpful. The generation profile can describe the technically possible or the actual generation of a plant. The feed-in profile refers to the power that actually flows into the grid. The difference becomes important when plants are curtailed, when part of the electricity is used on site as self-consumption, or when grid bottlenecks limit absorption. An example from German law: the online extrapolation of the transmission system operators, which forms the basis of the EEG market values, expressly disregards power reductions by the grid operator or within the framework of direct marketing. It therefore reflects a generation profile rather than a feed-in profile.

Residual load is consumption minus the feed-in of certain types of generation, usually wind power and photovoltaics. It shows what load still has to be covered afterwards by dispatchable power plants, storage, imports or load shifting. The generation profile of wind and sun is a central input for this. However, it does not determine residual load on its own, because the consumption profile and the chosen system boundary, such as a country, a bidding zone or a grid area, are equally important.

Why the timing of generation matters

An annual figure in terawatt-hours easily gives the impression that electricity generation is mainly a question of quantity. For fuel and climate balances and for expansion targets, annual quantities are indeed important. For the operation of the power system, however, they are not sufficient. In Germany, balancing groups are settled in quarter-hours. Since the delivery day of 1 October 2025, trading in the coupled European day-ahead market has also taken place in quarter-hours, with 96 prices per day instead of 24. This allows rapid changes in a generation profile, such as the morning and evening ramps of the PV curve, to be priced more precisely. If a lot of electricity is generated while demand is low and grids or storage are constrained, its immediate value falls. In scarcity hours, by contrast, the same kilowatt-hour can be worth considerably more.

The market value of a technology therefore results from its generation profile together with the price pattern. The EEG specifies this concretely: for onshore wind, offshore wind and solar, the spot market price for each quarter-hour is multiplied by the extrapolated generation. The sum is then divided by the total generation of the month or year. The result is a generation-weighted average price that enters the calculation of the market premium. The transmission system operators report the annual market values for 2025 as follows: the general annual average spot market price was 8.932 ct/kWh, the value for offshore wind 8.059 ct/kWh, for onshore wind 7.441 ct/kWh and for solar only 4.508 ct/kWh. The gap shows that with high build-out, photovoltaics depresses prices precisely in the hours in which it itself generates a lot. This effect is known as the cannibalization effect. For wind power, the market value depends on how many plants feed in at the same time and how well this feed-in matches demand, grid and balancing options. The market value reflects this time-related integration more accurately than a mere comparison of levelized costs of electricity.

The profile is also decisive for grids. A region with a lot of wind or solar capacity needs grid capacity not because of annual production, but because of simultaneous feed-in peaks. If many plants deliver high output under the same weather conditions, certain grid sections are heavily loaded. Grid planning and congestion management are therefore based on profiles rather than on average values. A line may be only lightly utilised on average, while individual hours decide on expansion or operational interventions. In Germany, the former feed-in management for renewable and CHP plants has no longer been regulated separately since 1 October 2021. It was merged with the redispatch of conventional power plants into so-called Redispatch 2.0.

Typical oversimplifications

Installed capacity is often confused with firm generation. A photovoltaic plant with a rated capacity of one megawatt does not deliver one megawatt continuously. Its generation follows the position of the sun and cloud cover. A wind turbine can contribute hardly anything in low-wind hours and a great deal in high-wind hours. Installed capacity is a technical upper limit under certain conditions. It says nothing about the time behaviour of generation.

A second oversimplification concerns full-load hours and the capacity factor. Both indicators relate annual generation to rated capacity. An example: a 1 MW plant that generates 2,000 MWh per year reaches 2,000 full-load hours. This corresponds to a capacity factor of about 23 percent, because the year has 8,760 hours. Such values are suitable for a rough comparison of sites or technologies. However, they do not reveal whether generation occurs in hours of high demand, during grid bottlenecks or at low prices. Two wind sites with similar full-load hours can therefore affect the system differently if their feed-in coincides to different degrees with that of other plants.

For dispatchable power plants, too, the profile is sometimes regarded as purely technically determined. In fact, their dispatch follows rules and incentives. A gas-fired power plant may be technically flexible, but it only runs if prices, fuel costs, CO₂ costs, availability and market rules trigger dispatch, or if it is needed for grid stability. For a coal-fired power plant, minimum load, start-up times, emission costs and the economic merit order shape the profile. The generation profile of dispatchable plants is therefore always also a result of market design and operating rules.

Generation mix, flexibility and system costs

A power system with a high share of renewable energy needs not only sufficient annual generation. It needs a generation mix whose profiles match demand, grids and balancing options. Wind power and photovoltaics partly complement each other, because in central Europe wind often blows more strongly in winter and at night, while the sun supplies electricity mainly in summer and at midday. This complementarity is, however, incomplete. There are hours in which both feed in strongly at the same time, hours in which both deliver little, and longer weather periods in which similar conditions over large areas limit the available output.

This gives rise to a need for flexibility. It can come from storage, dispatchable power plants, load shifting, electrolysers, heat storage, imports and exports, and from grid expansion. Which option fits depends on which problem the profile causes. PV midday peaks require different solutions than multi-day low-wind periods in winter. Battery storage can shift electricity over a few hours. Heat storage can decouple the operation of heat pumps in time. For rare, longer scarcity periods, firm capacities such as hydrogen-capable power plants are more likely to be considered. Looking at generation profiles helps avoid mixing these different requirements together in one general storage debate.

When assessing technologies, it is therefore important to separate plant costs from system costs. Low levelized costs of electricity of an individual technology do not automatically mean low total costs of the power system. If a profile causes high grid expansion costs, frequent curtailment, additional storage needs or low market values, these effects must be included. Conversely, a more expensive technology can be valuable for the system if it reliably feeds in during scarce hours or balances the profiles of other technologies.

The generation profile also touches several institutional levels. Support mechanisms influence whether plants are designed primarily for annual yield, for market value or for grid compatibility. One example is the reference of the EEG market premium to monthly or annual technology-specific market values. Grid charges, connection rules and regional price signals also help determine whether generation arises where it benefits the system. The electricity market sets price signals for scarcity and surpluses over time. However, it reflects grid bottlenecks within a bidding zone only to a limited extent. Redispatch and curtailment are then corrections in grid operation, which show that a generation profile does not readily fit the grid structure in space and time.

The term generation profile makes visible that electricity generation is a performance structured over time. It does not replace the view on costs, availability, grid connection, emissions or security of supply. But it prevents these questions from being reduced to annual quantities or installed capacity. Anyone assessing a power system should ask: When does a plant generate? How well does its feed-in match consumption? What balancing options exist? And which rules turn the technical possibility into actual feed-in?

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Edited by eCMS on 11.11.2026 19:47

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