Flexumer · Glossary

A flexumer is an electricity customer who can control the timing of their electricity consumption, self-generation or storage. In doing so, they respond to prices, grid requirements or other signals in the power system. The word combines "flexibility" with "consumer". A flexumer therefore does not merely draw electrical energy. They also provide the power system with loads that can be shifted, controllable feed-in or storage capacity. The term comes from the specialist debate and is not a legal term. There is no statutory definition in Germany.

What matters is not only how many kilowatt hours are consumed, but when electricity is consumed, fed in and stored. A heat pump may need the same amount of energy over the course of a day. However, it can move part of its operation into hours with plenty of solar or wind power. An electric car can charge immediately after being plugged in, or only when electricity is cheap or the distribution grid is under less strain. A battery can increase self-consumption, limit load peaks or feed in electricity when market prices are high. In all cases, a rigid load or feed-in becomes a variable quantity.

Distinction from consumer, prosumer and aggregator

A conventional electricity consumer draws electricity from the grid and uses it for household appliances, heating, mobility or business processes. Whether this consumption can be shifted in time plays no role for this role. For the power system, what matters with a conventional consumer is above all the load, that is, the power they are drawing at a given moment.

A prosumer consumes electricity and also generates it themselves, for example with a photovoltaic system on the roof. A prosumer does not have to be flexible, however. If the system simply feeds in whenever the sun shines and the household appliances run as always, there is self-generation but no active flexibility yet. The flexumer goes one step further: they coordinate generation, consumption and storage so that they respond to market or grid conditions.

An aggregator is also something different. An aggregator pools many small flexible assets and markets their flexibility on the electricity market, to grid operators or to balance responsible parties. The flexumer is the individual site where the flexibility arises technically and economically. A household with a battery and an electric car can be a flexumer. A service provider that controls thousands of such households is an aggregator.

Demand response does not mean the same thing either. It refers to demand responding to a signal, such as a price or a request to reduce load. Flexumers can make demand response possible. However, they can also act through storage, controllable feed-in or optimised self-consumption. The term flexumer is therefore broader than the mere shifting of loads.

Why flexumers are becoming more important in the power system

A power system with a high share of renewable energy needs more adjustment over time on the demand side. Wind and solar power depend on weather, time of day and season. In the past, it was mainly conventional power plants that adjusted their output to demand. With more photovoltaics, wind energy, heat pumps, electric cars and electrified industry, consumption, storage and grids take over part of this task.

Flexumers can help smooth the residual load. This is electricity demand minus the fluctuating feed-in from renewable energy. If many electric cars charge at midday, when a lot of solar power is generated, or heat pumps store heat ahead of a low-wind evening, less additional controllable generation is needed. In addition, flexumers can relieve the local grid if their systems do not all run at high output at the same time.

In practice, this matters above all in the distribution grid. New load peaks arise there from wallboxes, heat pumps and battery storage systems. A single electric car is usually not a problem for the power system. But if many cars in one street charge at the same time, this can put heavy strain on the local network transformer. Flexumers help make better use of the existing connection capacity. This does not replace grid expansion. However, it can influence how much is expanded, when and in which places first.

Flexumers also change demand on the electricity market. With a fixed energy price, the customer notices no difference between an hour with scarce generation and an hour with plenty of wind and solar power. Dynamic electricity tariffs, by contrast, pass the fluctuating spot market prices on to the customer. In Germany, all electricity suppliers have been required to offer such tariffs since 1 January 2025 (Section 41a EnWG). Previously this applied only to large suppliers. Anyone who wants to use a dynamic tariff needs an intelligent metering system. Suppliers must provide comprehensive information on costs, advantages and disadvantages. There is no entitlement to a contract with a particular supplier, because freedom of contract applies. A flexumer can only respond if the metering system, control, contract and devices fit together. Then the following applies: not every kilowatt hour is worth the same if its timing can be shifted.

Technical prerequisites

Owning a system does not automatically make someone flexible. A heat pump, an electric car or a battery storage system is only useful to the system if it is controllable, is metered and clear rules apply. This usually requires an intelligent metering system, controllable devices, energy management software and contracts that specify who may access which system and when.

In households and small businesses, this is hardly possible without automation. Almost nobody evaluates electricity prices, grid conditions and charging needs by hand every day. A flexumer is therefore often less a particularly active person than a connection with controllable devices and suitable rules. The person mainly decides which comfort limits should apply: When does the car have to be full? What room temperature is acceptable? How much battery capacity stays reserved for self-consumption?

Limits are set by storage capability, the requirements of a process and comfort. A cold store can only shift load as long as the temperature stays within narrow limits. A heat pump can store heat in the building mass or in a buffer tank, but not for an arbitrarily long time. An electric car is flexible as long as it is parked and sufficiently charged before the next journey. Flexibility is therefore not a freely available quantity of energy. It depends on time windows, power, duration and availability.

Economic and legal classification

Flexumers only help the system if the incentives match the task at hand. A dynamic electricity price mainly shows whether electricity is scarce or abundant on the wholesale market. It shows local bottlenecks in the distribution grid only in part. An hour with a low exchange price can nevertheless be critical in a particular local network if many systems are already charging there at the same time. Market price and grid need do not automatically coincide.

Whether flexibility is paid for, limited or not used at all depends on network charges, variable tariffs, the rules for controllable consumption devices and balancing. In Germany, Section 14a EnWG is particularly important. The Bundesnetzagentur (Federal Network Agency) set out the details in determinations of November 2023 (BK6-22-300 and BK8-22/010-A). They apply to controllable consumption devices in the low-voltage grid with a grid connection capacity of more than 4.2 kW that have been put into operation since 1 January 2024. These include private charging points, heat pumps, room cooling systems and battery storage systems that draw electricity from the grid. Participation is mandatory for them. Transitional rules apply to older systems with an existing agreement.

The grid operator may only temporarily throttle ("dim") the electricity draw of these devices if the grid is acutely overloaded or at risk of being damaged. It may not switch them off entirely. With direct control, at least 4.2 kW per device generally remains available. For large heat pumps or air conditioners above 11 kW, a higher minimum power applies. In return, the grid operator may no longer refuse the connection of such devices by pointing to a threatened grid overload. In addition, the customer pays lower network charges. Module 1 is a flat-rate reduction. With Module 2, the energy price component of the network charge falls by 60 percent, but a separate meter is required. Since 1 April 2025 there has also been Module 3 with time-variable network charges, which can be combined with Module 1. Section 14a EnWG is not a marketing of flexibility in the narrow sense. It gives the grid operator a right to intervene and gives the customer compensation for it. Only Module 3 creates a genuine price incentive to move consumption to times of low grid load.

Anyone who wants to understand the effect must look at the rule to which a flexumer responds. They do not respond abstractly to "the system", but to concrete prices, control commands, contractual conditions or default settings in the devices. If these signals contradict each other, false incentives arise. A household can operate its battery so that self-consumption rises, even though feeding in at another time would be more useful for the overall system. A dynamic tariff can lead to many cars charging at the same time because all devices respond to the same low prices. Flexibility therefore needs coordination, not just devices.

Typical misunderstandings

Flexumer is often equated with self-sufficiency. However, a high degree of self-consumption and independence from the grid are different goals from flexibility that benefits the system. A battery can reduce a household's electricity draw from the grid without relieving the grid. It can even create new load peaks if it charges in the same cheap hours as many other storage systems. Flexumers are particularly valuable when their control takes account of the grid and the market and not just their own electricity bill.

A second misunderstanding regards flexibility as a free reserve. Flexible consumers, however, incur costs. Charging later can restrict comfort. Frequent charging and discharging ages storage systems. In industry, shifting loads can change production processes. Anyone who wants to integrate flexumers fairly therefore needs remuneration, clear liability and transparent rights of intervention. Otherwise flexibility is expected politically but not reliably delivered in practice.

A third misunderstanding overestimates how well private households can be controlled. Many flexible potentials are small, irregular and depend on everyday life. Their effect only becomes noticeable in large numbers and usually through automatic pooling. Flexumers therefore do not replace firm capacity in the simple sense. They can reduce load peaks, ease bottlenecks and reduce the need for peaking power plants. However, they do not guarantee that a certain capacity is available at every point in time, as long as there are no suitable contracts, measurements and sanctions.

Relationship to storage, market and security of supply

Flexumers stand where flexibility, storage, the electricity market and grid operation meet. They show that security of supply does not depend only on power plants. Demand can also contribute if it can be adjusted in time. Responsibilities remain distributed in the process: the grid operator ensures safe grid operation, the supplier procurement and billing, the metering point operator the metering technology. The customer uses their system within the agreed rules.

The difficulty is to link these responsibilities without the same system being controlled from several sides. An electric car can offer the household mobility, enable the supplier to purchase cheaply, be a controllable load for the grid operator and become part of a virtual power plant for an aggregator. These roles can fit together, but they can also contradict each other. Conflicts arise where technical possibilities, market rules and responsibilities do not fit together.

The term flexumer is useful if it is used precisely. It does not describe a new type of person or an automatic solution to grid bottlenecks or periods of low wind and sun (Dunkelflauten). It refers to an electricity customer whose consumption, generation or storage can be adjusted in time. This ability only acquires value through metering, control, rules and remuneration. The flexumer matters for the power system because they no longer treat consumption, generation and storage as fixed quantities, but as controllable contributions within technical and economic limits.

Sources

§14a EnWG Steuerbare Verbrauchseinrichtungen – Integration von steuerbaren Verbrauchseinrichtungen — Bundesnetzagentur; unbekannt. Verbraucherportal Energie, Abschnitte zu Anwendungsbereich, Dimmen und Mindestleistung
Steuerbare Verbrauchseinrichtungen nach § 14a EnWG — N-ERGIE Netz GmbH; unbekannt. Abschnitt zu den Netzentgelt-Modulen
Dynamische Stromtarife — Bundesnetzagentur; unbekannt. Verbraucherportal Energie, FAQ zu dynamischen Stromtarifen
§ 41a EnWG – Lastvariable, tageszeitabhängige oder dynamische und sonstige Stromtarife sowie Festpreisverträge — buzer.de (Gesetzestext nach BGBl.); Fassung durch Gesetz vom 18.12.2025 (BGBl. 2025 I Nr. 347), gültig ab 23.12.2025. § 41a Abs. 1 und Abs. 2 Satz 2 EnWG

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Edited by eCMS on 12.11.2026 05:05