Hidden Flexibility · Glossary

Definition

Hidden flexibility (in German: versteckte Flexibilität) refers to options for adjusting electricity consumption, generation or storage that exist technically but do not appear in the power system as an available resource. A facility can shift its electrical load in time, briefly reduce it, increase it or otherwise operate differently without giving up its actual purpose. As long as this capability is not measured, made controllable, contractually regulated or remunerated, it remains hidden. The term is not a defined legal term but a descriptive technical term. Nor does it refer to a single technology, but to the gap between what is technically possible and what the system can actually use.

Some examples: A cold store can run its refrigeration plant earlier and pause it later. A heat pump can, within certain limits, heat earlier if the building and storage have enough thermal inertia. An electric vehicle often does not need to charge at full power immediately. It only has to be sufficiently charged by a certain point in time. An industrial plant can postpone a process step if production planning, quality assurance and staff deployment allow it. In all these cases, flexibility is a property of the application, but not automatically a product that can be called upon.

Parameters: more than a kilowatt figure

Hidden flexibility is usually described by several quantities: the electrical power in kilowatts or megawatts, the shiftable amount of energy in kilowatt-hours or megawatt-hours, and time parameters. The time parameters include lead time, response speed, maximum duration of the adjustment, recovery time and the frequency of possible interventions. A flexible load of 100 kilowatts says little on its own. Only the duration makes it comparable: 100 kilowatts over two hours corresponds to 200 kilowatt-hours of shifted energy, over five minutes only about 8 kilowatt-hours. The direction is also important. Some facilities can reduce load, others can absorb additional load, for example when a lot of solar power is present in the local grid.

Distinction from related terms

Hidden flexibility differs from flexibility in the general sense in that it has not yet been made ready for use. Flexibility is the ability to adjust feed-in, consumption or storage in time. Hidden flexibility is the part of this ability that is reliably available neither in the market nor in grid operation. It may be presumed, technically plausible or demonstrated in pilot projects, but it cannot be planned and called upon in normal operation.

The term must also be distinguished from demand response. Demand response is the organised reaction of consumers to price signals, calls or contractual requirements. Hidden flexibility lies one step before that. It is the raw potential that can become demand response only through metering systems, control technology, pooling, tariffs, contracts and clear responsibilities. A household with a heat pump may possess flexibility. Demand response arises only when it can be activated according to fixed rules and the user knows the restrictions, benefits and responsibilities.

Hidden flexibility is also not a synonym for storage in the narrower sense. A battery storage system takes in electricity and releases it again later. Many flexible applications, by contrast, store not electricity but utility: cold in refrigerated goods, heat in a building, state of charge in a vehicle battery or intermediate products in an industrial process. This shifting can be similarly valuable to the power system as storage, but follows different limits. Comfort, product quality, battery condition, maintenance, warranty and operational procedures set real constraints.

Finally, hidden flexibility must not be confused with energy efficiency. Efficiency reduces the energy needed for a given service. Flexibility, by contrast, changes the timing or level of power consumption. An efficient heat pump can be operated inflexibly if it reacts immediately to every temperature deviation. A less efficient system can be flexible in the short term if it has a buffer. Both properties can coincide, but do not have to. Kilowatt-hours and kilowatts describe different problems.

Why the topic is becoming more important

Generation and consumption diverge more strongly in space and time. Wind and solar power feed in depending on the weather. Heat pumps, electric vehicles and new industrial applications increase electricity demand and change load profiles. In the distribution grid, these changes appear locally. A street with many charging points, a commercial area with photovoltaics or a village grid with heat pumps can reach the limits of cables or transformers at certain times, even though enough generation is available in the overarching system.

A great deal of hidden flexibility lies precisely in the distribution grid, because many small facilities are connected there. Its effect, however, is location-bound. A flexible heat pump relieves a bottleneck only if it is located in the affected grid section. A battery can be useful for the wholesale market and still do nothing for a local grid problem if it is connected at the wrong place or is already earmarked for another purpose. Hidden flexibility is therefore not an abstract megawatt figure. Its value depends on location, timing, grid situation and the reliability of the call.

Not a free reserve stock

A common misunderstanding is to treat hidden flexibility as a free reserve. That a facility is technically adjustable does not mean it can be used without costs, risks or restrictions. Anyone who postpones an industrial process changes production planning and possibly delivery capability. Anyone who reduces charging power must still meet mobility needs. Anyone who controls heat pumps touches comfort limits and building physics. Conversely, a shift can be valuable even if consumption does not fall overall. It can avoid a grid peak or absorb electricity in times of high renewable feed-in. The benefit then lies in the timing, not in saved energy.

Institutional reasons for remaining hidden

Flexibility often remains hidden because responsibilities are separated. Grid operators see grid loads, but may intervene in their customers' facilities only on a legal or contractual basis. Suppliers and direct marketers react to wholesale prices, but know local grid restrictions only to a limited extent. An aggregator can pool many small facilities. To do so, it needs access to data, control and settlement. Customers own the facilities and want understandable rules rather than technical complexity. A technically simple load shift can therefore become organisationally demanding.

Instruments for tapping potential (legal status Germany and EU, November 2026)

Various instruments are intended to make such potentials usable. Each sets different incentives and applies only to certain facilities.

Grid-oriented control under § 14a EnWG (Germany): Under the determinations of the Bundesnetzagentur, controllable consumption devices have had to be dimmable since 1 January 2024. This refers to newly connected heat pumps, private charging devices, space cooling systems and electricity storage systems in the low-voltage grid with a grid connection capacity of more than 4.2 kW. The grid operator may reduce electricity consumption only temporarily and only in the event of imminent overload or damage to the grid. A minimum power of 4.2 kW is retained. In return, there are reduced grid charges. The rule thus above all makes grid-serving flexibility of small loads accessible.
Dynamic electricity tariffs under § 41a EnWG (Germany): Since 1 January 2025, in principle all electricity suppliers must offer final consumers with a smart metering system a dynamic tariff. Previously, the obligation applied only to suppliers with more than 100,000 customers. Such a tariff rewards reacting to exchange prices, but not automatically relieving local grid bottlenecks.
Procurement of flexibility by distribution system operators (EU): Under Article 32 of the Electricity Market Directive (EU) 2019/944, Member States are to create a legal framework that allows distribution system operators, and gives them incentives, to procure flexibility services, including congestion management. In principle, this is to be done through transparent, non-discriminatory and market-based procedures. The concrete implementation, for example via local flexibility markets, differs from country to country and is not complete everywhere.

These instruments can interfere with one another. An aggregator that markets a facility must avoid it being scheduled simultaneously for balancing group management, grid relief and self-consumption optimisation without conflicts being resolved. Grid-oriented control gains acceptance only if interventions are limited, comprehensible and compensated.

Assessment and limits

Hidden flexibility shows that the transformation of the power system depends not only on generation plants and lines. It also depends on whether millions of consumption and storage facilities are integrated in such a way that their leeway becomes usable without impairing their purpose. Tapped flexibility can reduce grid peaks, lessen the curtailment of renewable plants, dampen system costs and support security of supply. It cannot, however, provide energy that is permanently lacking. Nor does it replace necessary grid expansion, firm capacity for long periods of low wind and sunlight (Dunkelflauten), or clear market rules.

Anyone who uses the term precisely avoids exaggerated expectations. Hidden flexibility is not an available reserve as long as it merely lies dormant in devices, processes or buildings. It becomes a resource only when technical controllability, reliable data, suitable contracts, clear responsibilities and economic incentives come together. The term describes the distance between what facilities could physically do and what the power system can actually use under real rules.

Sources

§14a EnWG Steuerbare Verbrauchseinrichtungen – Integration von steuerbaren Verbrauchseinrichtungen — Bundesnetzagentur; unbekannt. Verbraucherportal Energie, Abschnitte zu Anwendungsbereich und Dimmen
Dynamische Stromtarife – Vertragsabschluss — Bundesnetzagentur; unbekannt. Abschnitt zu dynamischen Stromtarifen, Hinweis auf § 41a EnWG
§ 41a EnWG – Lastvariable, tageszeitabhängige oder dynamische und sonstige Stromtarife — gesetze.legal (Wiedergabe des Gesetzestextes, Bundesrecht); unbekannt. § 41a Abs. 2 EnWG
Richtlinie (EU) 2019/944 über gemeinsame Vorschriften für den Elektrizitätsbinnenmarkt, konsolidierte Fassung — Europäische Union, EUR-Lex; 2024-07-16 (konsolidierte Fassung). Artikel 32 Absatz 1

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Edited by eCMS on 12.11.2026 05:06