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Glossary · Energy industry & energy transition

Self-consumption rate

Self-Consumption Rate Self-Consumption photovoltaics prosumer Battery storage Degree of self-sufficiency electricity consumption

Definition

The self-consumption rate, also called the self-consumption share, indicates what share of self-generated electricity is used at the place of generation. For a photovoltaic system, it shows how many of the kilowatt-hours generated do not flow into the public electricity grid. Instead, this electricity is used in the building, on the property or within a permissible local consumption arrangement. In the widely used definition of HTW Berlin, self-consumption includes solar electricity consumed at the same time as it is generated as well as electricity charged into the owner's own battery storage. The higher the rate, the less solar electricity is fed into the grid.

Calculation and units

The self-consumption rate is the ratio of self-used electricity to the total electricity generation of the system over a defined period, usually a calendar year. An example: a photovoltaic system generates 10,000 kilowatt-hours per year. Of this, 3,500 kilowatt-hours are used directly in the house or charged into the storage. The self-consumption rate is then 35 percent, and the remaining 6,500 kilowatt-hours are fed into the grid. Electricity that is curtailed, for example because of a limit on feed-in power, is never generated in the first place. It is therefore not included in the measured generation, and so not in the denominator of the rate. Anyone who instead calculates with possible generation must state this explicitly, otherwise the values are not comparable.

The rate itself has no unit; it is expressed as a percentage. The underlying energy quantities are measured in kilowatt-hours. This is a quantity of energy and not the instantaneous power in kilowatts. A system with a rated power of 10 kilowatts delivers very different amounts of energy per year depending on location, orientation, weather, shading and mode of operation. The balancing period is also important: an annual rate averages sunny summer days and dark winter days. Monthly or daily values can deviate strongly from it.

Distinction from the degree of self-sufficiency

The self-consumption rate relates to generation. It answers the question: what part of my own electricity production is used by myself? The degree of self-sufficiency, by contrast, relates to consumption. It asks what part of total electricity demand is covered by the household's own system including storage, whether directly or from the battery. Both metrics have the same numerator, the self-used solar electricity, but different denominators. An example: a household consumes 5,000 kilowatt-hours, its system generates 10,000 kilowatt-hours, and it uses 2,000 kilowatt-hours of that itself. The self-consumption rate is then 20 percent and the degree of self-sufficiency is 40 percent.

The two values often move in opposite directions. With a small system, almost every kilowatt-hour generated is consumed immediately. The self-consumption rate is then high, but the degree of self-sufficiency is low. A large system can increase the degree of self-sufficiency, but in doing so it lowers the self-consumption rate, because in many hours it generates more than is needed on site. An example from the Verbraucherzentrale Rheinland-Pfalz on a study by HTW Berlin shows this: in a single-family house with a heat pump, both metrics are initially 28 percent. With significantly lower consumption and comprehensive renovation, around 80 percent self-sufficiency is possible, while the self-consumption share rises only to 38 percent. Anyone who wants to increase the self-consumption rate uses the generation as simultaneously as possible or stores it temporarily. Anyone who wants to increase the degree of self-sufficiency must cover consumption themselves in as many hours of the year as possible, including in winter and at night.

Influencing factors: simultaneity, load profile and storage

Self-consumption arises mainly when generation and consumption occur at the same time. Solar electricity generated at midday can only be used directly if appliances are running at that time. These can be household appliances, a heat pump, charging points for electric vehicles, commercial processes, cooling, ventilation or electric water heating. Annual electricity consumption alone is therefore not sufficient for an assessment; the load profile is decisive. Two households with the same annual consumption can achieve very different rates if one uses electricity during the day and the other mainly in the evening. For commercial businesses with a daytime load, such as supermarkets, offices or workshops, solar generation often matches consumption better than in a classic household. Heat pumps and electric cars raise the rate above all when their operation is controlled in terms of timing, for example by an energy management system. Without control, they initially mainly increase total consumption.

A battery storage system shifts part of the midday generation to the evening or night. As usable storage capacity increases, both the self-consumption rate and the degree of self-sufficiency therefore rise. However, additional storage capacity brings less and less benefit. The storage does not generate additional electricity; it only changes the time of use and causes conversion losses. Since, under the HTW definition, even charging the battery counts as self-consumption, these losses are contained in the self-consumption rate. A high rate therefore does not mean that every self-used kilowatt-hour has actually replaced a purchase from the grid.

Economic and systemic assessment

Economically, what matters most to the system operator is the difference between the avoided costs of electricity from the grid and the feed-in tariff or the market value of the electricity fed in. If the household electricity price is well above the tariff, self-consumption is particularly worthwhile. HTW Berlin pointed out early on: if the tariff falls to the market price level, feed-in revenues hardly contribute to refinancing any more, and systems with a high self-consumption share become more important. This view is coherent for the operator, but it does not reflect all costs and services of the electricity system. Grid charges, levies, taxes and duties partly depend on the kilowatt-hour drawn from the grid. Depending on regulation, self-consumption can therefore shift the financing of the shared grid infrastructure onto other consumers. That does not make self-consumption wrong. But it shows that its evaluation also depends on rules and not only on technology.

A higher self-consumption rate is therefore not a pure measure of efficiency. Solar electricity fed into the grid is available to other consumers and can displace other generation there. What is more favourable for the economy as a whole depends on the grid situation, market prices, storage losses and the time value of the electricity. For the grid, quarter-hour values, feed-in and withdrawal power, voltage maintenance and the question of how many systems feed in at the same time also count. An annual rate is only a rough indication of this. It says nothing about peak withdrawal power: a household can use a lot of its own electricity on an annual average and still draw high power from the grid on cold winter evenings. A storage system that always charges immediately when there is a surplus is often already full before the midday peak and then hardly reduces feed-in peaks. Only operation that responds to forecasts, dynamic prices or signals from the grid operator can provide flexibility for the system. The self-consumption rate does not recognise this difference.

A common misconception equates a high self-consumption rate with independence from the grid. Even a household with photovoltaics and storage is generally not an island grid. It uses the public grid to deliver surpluses, to draw electricity at night and when generation is low, and for stable voltage and frequency within the interconnected system. Studies by HTW Berlin and the Verbraucherzentrale also conclude that even energy-efficient buildings cannot be operated fully self-sufficiently with solar energy.

Legal framework in Germany (as of November 2026)

Not every local use of electricity is treated the same in legal terms. It makes a difference whether the operator consumes electricity from their own system themselves, whether several parties in a building are supplied, for example under tenant electricity supply (Mieterstrom), whether a customer installation (Kundenanlage) exists, or whether electricity is conveyed through the public grid. Until the end of 2022, the EEG defined self-supply narrowly: the operator of the system consumes the electricity themselves, in the immediate vicinity and without conveyance through a grid. At that time, this concept was important for the EEG surcharge. Since 1 January 2023, the surcharge rules on self-supply in the EEG have been abolished, and self-supply is possible without the EEG surcharge. According to the German federal government's explanatory memorandum, no more levies should in future be incurred on self-consumption and direct supply behind the grid connection point. Metering concepts, supplier obligations, billing, grid charges and tax issues can nevertheless make a technically simple solution legally demanding.

In addition, rules on feed-in apply to new photovoltaic systems that have an indirect effect on the self-consumption rate. Under Section 9 EEG 2023, certain systems below 25 kilowatts that receive a feed-in tariff or the tenant electricity surcharge (Mieterstromzuschlag) must limit their feed-in at the grid connection point to 60 percent of the installed capacity. This rule applies to systems commissioned since 25 February 2025, and until the intended metering and control technology has been installed. For the same new systems, the payment for electricity fed in no longer applies during periods of negative exchange prices. Both can make it more attractive to use electricity oneself or to store it temporarily. Which obligations apply in an individual case depends on the date of commissioning, the system size, the form of marketing and the metering technology.

Conclusion

Properly understood, the self-consumption rate is a useful metric. It shows how closely generation and local consumption coincide or are brought together by storage and control. It does not show how independent a consumer is, how grid-supportive a system operates, what costs arise in the overall system, or whether electricity fed into the grid would be worth less than self-used electricity. Anyone who uses the term precisely separates the share of generation, coverage of consumption, power demand and legal classification. Only then does it become clear which technical decision, which economic effect and which energy-economic question is actually at issue.

Sources

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Edited by eCMS on 11.11.2026 19:42

© 2026 Erik Schmidt. All rights reserved. Quotations with a link to the source are welcome.