The Federal Network Agency (Bundesnetzagentur) issued its determination on market integration of storage facilities and charging points (Marktintegration von Speichern und Ladepunkte, “MiSpeL”) on 1 October 2026, putting an important part of electricity storage facility regulation in place at last. The detailed rules put an end to the strict distinction between green solar power and grey electricity from the grid, and their technical and settlement provisions should give electricity storage facilities more flexibility in future.
Background: the strict distinction between green and grey electricity
Up to now, electricity storage facilities have only been able to obtain support under Germany’s Renewable Energy Sources Act (Erneuerbare-Energien-Gesetz, “EEG”) if they draw on section 19(3a) EEG 2023, known as the “exclusivity option” (Ausschließlichkeitsoption). Under this option, electricity fed in from a storage facility has only been eligible for support if the renewable energy installation stored green electricity exclusively. There was otherwise a risk that non-eligible grey electricity would receive support via the storage facility, as it is impossible to distinguish electricity stored from different sources without metering it separately. Eligibility for support could therefore be jeopardised by even small quantities of grey electricity – in particular, electricity drawn from the grid. But charging from the grid is a key economic advantage for storage facilities. A facility limited to storing solar or wind power generated on-site can only charge when those installations are generating electricity. If it is also allowed to draw electricity from the grid, however, it can opt to charge at times when the wholesale electricity price is lower or even negative, and feed the electricity back into the grid later when prices rise (“arbitrage”), provide ancillary services (especially on the balancing energy market), and level out peaks in offtake. For the most part though, operators of storage facilities combined with renewable energy installations that receive support have been unable to tap into this flexibility, as they have been forced to choose between EEG support or relying on the market.
Operators have also had to choose between EEG support and surcharge relief. Section 21 Energy Financing Act (Energiefinanzierungsgesetz, “EnFG”) gives electricity drawn from the grid, temporarily stored and then fed back in an exemption from EnFG surcharges (specifically, the Combined Heat and Power Act (Kraft-Wärme-Kopplungsgesetz) and offshore grid surcharges). This is to prevent double-surcharging of electricity, once when stored, and then later during final consumption. So operators had two options: either they stored green electricity exclusively and secured EEG support for it, or they also charged with electricity from the grid (exempted from the surcharge), losing EEG support for stored electricity in the process. It was impossible to combine the two benefits.
New options for multi-use storage facilities
The Bundesnetzagentur has now abolished the strict distinction between green and grey electricity. From now on, not only entirely green electricity storage facilities but also multi-use storage facilities will be eligible for pro rata EEG support and surcharge relief, with operators being able to choose between the separation option and the flat-rate option. The MiSpel determination sets out the metering and calculation models for deciding what share of stored electricity comes from the renewable energy installation and what share comes from the grid.
Separation option: This option distinguishes the stored electricity on the basis of meter readings. Metering systems compliant with calibration law record offtake and feed-in plus charging and discharging of the storage facility in 15-minute intervals. The stored electricity is then classified pro rata as green electricity or as electricity from the grid. The requisite meter configuration will depend on the specific installation, which might be a standalone battery energy storage system (“BESS”), a BESS system combined with a photovoltaic system, or a one-off form of co-location, for example. The determination sets out detailed metering concepts for a large number of standard scenarios. A typical combination of photovoltaic system and storage facility generally requires two metering devices: a bidirectional meter at the grid connection point for offtake and feed-in plus a second meter to measure charging and discharging in the storage facility directly. Standalone electricity storage facilities – not combined with a generating installation – need only one metering device at the grid connection point, reducing the technical and bureaucratic requirements significantly. The Bundesnetzagentur only included these facilities in the scope of the MiSpeL determination after this was suggested during the consultation. So standalone storage facilities will be able to use the separation option for surcharge relief.
Practical tip: The metering concept is crucial to the separation option. Operators should decide on a suitable metering and balancing concept with grid and meter operators as well as direct marketers as soon as possible, checking whether existing installations need to be retrofitted.
Standardised formulas are used to work out the source and destination of the electricity, based on the readings. EEG support is paid for electricity directly fed in from the renewable energy installation as well as for temporarily stored green electricity. Temporarily stored electricity from the grid, by contrast, enjoys surcharge relief under section 21 EnFG if it is fed back into the grid. There are also strong indications that the calculation methodology provided for in the MiSpel determination will also apply, at least indirectly, to the network tariff exemption for temporarily stored electricity from the grid, as section 118(6) Energy Industry Act (Energiewirtschaftsgesetz) refers to section 21 EnFG. That said, the Bundesnetzagentur is currently giving the network tariff system a complete overhaul in the shape of the AgNes procedure (General Electricity Network Tariff System, Allgemeine Netzentgeltsystematik Strom). It is therefore likely that electricity storage facilities will lose their network tariff exemption. In this case, the MiSpeL determination’s calculation methodology would then remain relevant – at most – to existing installations and those protected by the principle of legitimate expectations.
- Flat-rate option: The determination offers a simpler alternative for smaller installations such as those typically operated by private individuals or small businesses. It can be used by storage facilities combined with solar installations whose total installed capacity does not exceed 30 kilowatts of peak power (“kWp”). The basic issue is the same as in the separation option: If the storage facility feeds electricity into the grid, there is no way of knowing whether that electricity is temporarily stored solar power (for which the EEG market premium is paid) or temporarily stored electricity from the grid (which is exempted from surcharges). Under the flat-rate option, annual feed-in is not metered but divided up in line with fixed limits. Up to 500 kWh per kWp of installed solar capacity counts as solar power and is eligible for the market premium. Above a second limit – calculated according to a fixed formula – the electricity fed in counts as temporarily stored electricity from the grid, and this excess amount is exempted from surcharges. Quantities falling between the two limits are not eligible for either support or exemption from surcharges. The trade-off is that a single bidirectional meter exact to within 15 minutes is sufficient. Operators of solar installations that do not receive support may also opt for surcharge exemption above the second limit.
Whatever option is chosen, the relevant distribution system operator needs to be informed. If the installation is directly marketed, the direct marketer must support the selected option. In addition, any technical alterations will need to be registered with the Master Market Data Register (Marktstammdatenregister).
What MiSpeL means for charging points
The determination also addresses bidirectional charging points, i.e. wall boxes or EV chargers that can be used to feed electricity from the vehicle battery back into the grid (vehicle-to-grid) or into the customer’s private installation (vehicle-to-home). Until now, any temporary storage in charging points was not eligible for support, either in general or specifically through the exclusivity option, which is only open to storage facilities restricted to renewable energy. EV batteries are not storage facilities in this sense, because vehicles can draw electricity from the grid at other charging points as well. So neither EEG support nor surcharge relief was available to electricity fed back into the grid from vehicle batteries. The only way for operators of solar installations with a bidirectional wall box to obtain support for directly fed-in solar power was to take appropriate technical measures to stop vehicles from simultaneously feeding electricity back into the grid. Both new options in the MiSpel determination largely treat bidirectional charging points as storage facilities: green electricity fed back into the grid can receive pro rata support, while electricity from the grid that is later fed back in can be netted against surcharges.
Significant gains, implementation pains
Viewed as a whole, the determination is a major step forward. The separation option is important for operators of solar and wind parks co-located with storage facilities, as well as for commercial and industrial storage facility operators: it lets them align their installations with the market (i.e. charge from the grid when electricity is cheap and feed in when it is in short supply) without losing EEG support for green electricity or the surcharge benefits for arbitrage. Another positive development is the specific and detailed metering concepts the Bundesnetzagentur has set out for a multitude of standard scenarios, establishing legal and planning certainty and facilitating agreement with grid and meter operators. Many will also welcome the Bundesnetzagentur’s incorporation of key suggestions raised during the consultation, such as the inclusion of standalone storage facilities, in the determination.
But the separation option is complex: implementation of its formulas, metering concepts and obligation to standardise balancing will place considerable demands on installation operators, direct marketers as well as grid and meter operators. For this reason, operators should decide on a suitable metering and balancing concept with all parties involved as soon as possible, checking whether existing installations need to be retrofitted.
Outlook and transition period
The determination entered into force upon publication. A transition period will apply until 30 September 2027, however, during which the new options can only be used with the consent of grid and meter operators. From 1 October 2027, they will be obliged to facilitate such use. And a further restriction applies to the flat-rate option: eligibility for both EEG support and surcharge netting will only take effect from the month following State aid approval by the European Commission.
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