Grid compatibility test (NVP) for large-scale PV systems

The integration of solar systems into the public electricity grid is a complex process that requires careful planning and coordination. A central step in this process is the Grid compatibility test (NVP) for large-scale PV systemswhich is carried out by the grid operator before the start of construction. This test ensures that the feed-in of solar power has no negative impact on grid stability and reliability. The commitment is Mandatory for systems with an output from 30 kWp and is usually the starting signal for a PV project. Early contact between the company carrying out the project and the regional energy supply company or grid operator is therefore crucial to ensure smooth processing. The NVP is generally valid for six months, during which the system should be completed. However, an extension is usually not a problem for large-scale PV projects.

Relevant information prior to the grid impact assessment

As soon as the planning and design of the large-scale PV system have been completed, the system operators must always submit the highest output of the entire system for the NVP. One Subsequent change in performance is only downwards and not upwards possible. If additional areas or extensions to the photovoltaic system are desired after the documents have been submitted, a new or further NVP must be applied for. Planners and operators should also urgently take into account the processing time between the submission deadline and the result of the grid compatibility assessment in the project plans. The grid operators' analyses currently take between four to 15 weeksuntil a positive NVP is available. The feed-in commitment then usually follows quickly after a positive grid compatibility test.

Documents required for the grid impact assessment

The documents to be submitted for an NVP are not regulated by law and vary from grid operator to grid operator. In case of doubt, they provide information on the documents required for the grid compatibility assessment. These documents are usually mandatory:

• Site plan of the property including the buildings, open spaces and parking lots to be occupied
• General plan of all planned PV systems with kWp data and Circuit diagrams incl. all existing grid connections
• Declarations of conformity of the planned Inverter, technical data the Solar modules and, if provided, Data sheets the Battery storage
• Written Consent of the Landowner for the construction of the large-scale PV system

Steps in the network compatibility assessment (NVP)

Once the documents have been submitted, the grid operator uses the data to determine the optimum feed-in point. Economic efficiency is the most important aspect in this calculation of the so-called connection point of large-scale PV systems with the public grid. After the total peak power of the modules, the grid operator checks the effects of the planned PV system on grid stability, security and capacity. In the best case, such a suitable connection point is already located directly on the company premises or the existing grid connection is even sufficient.

Especially for large-scale PV systems planned in Regions with high PV density or with low grid reserves however, this is usually not the case, meaning that the grid operator has to expand its grid capacity. Such integration then requires the laying of additional cables and the construction of further infrastructure, which necessitates additional approvals and agreements. This delays the entire grid compatibility assessment process, as grid operators have to wait for such a PV project to be approved. Calculate separately must.

It becomes particularly complex, for example, if the allocated feed-in point is located on the territory of an uninvolved third party. In such a case, it is not only necessary to reach an agreement with the landowner, but it may also be necessary to process a License agreement with the relevant authorities or institutions. Accordingly, a detailed understanding of local conditions and the legal framework as well as intelligent PV planning are essential in order to overcome potential obstacles.

If the company's electricity grid has not yet RLM meter If the meter is already installed, the new large-scale PV system operator will receive a bidirectional meter near the transfer point from the energy supplier at the latest after the commitment to feed into the grid. The location for this should be specified in the contract. This RLM meter measures the supply and feed-in current every quarter of an hour, is rented from the grid operator for an annual fee and is offset against the supply contract. It is part of a smart metering system, can be controlled remotely and is mandatory nationwide in accordance with the Electricity Grid Access Ordinance (StromNZV). Find out more in our article "Smart meters: Long standard in the industry“

What happens in the event of a negative grid compatibility test (NVP) for large-scale PV systems?

In certain cases, the grid operator can refuse to connect a large-scale PV system to the grid, as stipulated in EEG Section 9 (3). This refusal can occur if the costs for a grid expansion amount to more than 25 % of the system costs. This is particularly possible in regions with a high density of PV systems, such as southern Germany, where the existing grid is already fully utilized.

In such situations, the applicant is initially at a disadvantage. The Clearing center EEG/KWKG and the amendment to the EEG now stipulate that the grid operator must provide proof of the costs for grid expansion. Nevertheless, the distribution grid operator (DSO) is granted a reasonable period of time to adapt its grid to the additional loads. According to EEG Section 9, it must ensure the "immediate" provision of a connection, which means that it must not cause any culpable delays.

The grid operator may not refuse the feed-in commitment without further ado. According to the legal requirements, the connection and feed-in of a large-scale PV system must be economically reasonable for the grid operator. Even if it does not have sufficient capacity of its own to expand the grid, it must outsource the necessary work. In such a case, the grid operator is obliged to take all necessary measures to minimize the delay and guarantee the feed-in commitment. It must document and disclose this.

Distribution of expansion costs

In accordance with the provisions of the EEG, the Grid operator obligedto purchase solar power from photovoltaic systems. The feed-in should generally be guaranteed via the house connection, whereby the system operator bears the costs of the electrical installation to the nearest feed-in point. However, if this feed-in point is further away, the energy supplier must bear the additional costs incurred.

At the end of 2023, the Clearing House published a recommendation on "Cost allocation for the grid connection of PV systems". Comments from the Federal Network Agency, the BDEW and other associations were taken into account. The recommendation mainly deals with PV systems in the low-voltage range, but also covers applications in the medium-voltage range. It reaffirms that, according to the EEG, the entire area upstream of the house connection box is the responsibility of the grid operator.

This has an impact on the distribution of costs, which are mainly borne by the grid operator in accordance with Section 16 of the EEG. This includes work in connection with the connection of the renewable energy system to the grid connection point, IT integration and the review of documents in accordance with Section 10 (2) EEG. The regulation of construction cost subsidies in accordance with Section 11 NAV does not apply to feed-in RE systems whose connection is based exclusively on the EEG. Flat-rate costs are only permissible if they transparently and clearly show the costs in accordance with the responsibilities.

Costs for a network compatibility test (NVP)

In principle, grid operators may not charge any costs for initial inquiries for a grid compatibility check, as stipulated by the EEG/KWKG clearing house. They name either suitable and existing or favorable and technically economical connection points to the system operators willing to feed in. These can be located on or near the property to be tested. However, extended grid compatibility assessments with calculations for a necessary grid expansion and second grid compatibility assessments, which become necessary in the event of a change of plan for a larger PV system, are subject to a charge.

Start of construction due to positive NVP decision

Usually, a positive grid compatibility assessment (NVP) means that a planned energy project meets the requirements and standards to be integrated into the existing electricity grid without causing undesirable effects on grid stability or security of supply. If an NVP is positive, the Developer of the project with the Start implementation. Only after completion does the network operator test then follow in accordance with VDE-AR-N 4110 in the medium voltage. This is where delays occur more and more frequently.  

What happens if the feed-in commitment is delayed?

Completed large-scale PV systems without a grid operator inspection and without a feed-in commitment can of course go into operation. However, the green electricity can then be initially only for own use are used. Surplus energy is locked up and dissipates, which is increasingly becoming a risk for photovoltaic investments in Germany because the Lack of feed-in revenues. On the one hand, there is clearly a lack of necessary grid expansion and, on the other, a lack of capacity for certification.

In the Years 2023 there was Almost 900 completed PV systems over 700 kWp that have not yet undergone a grid operator inspection. Most of these systems are located in the new federal states, and a backlog of inspections is being observed with suspicion. Everything indicates that the grid operators are unable to keep pace with the increasing number of new PV systems. For example, around 2.3 billion euros of private investment is tied up as these large-scale PV systems have not generated any feed-in revenue for at least a year.

Conclusion

The grid compatibility assessment (NVP) process for large-scale PV systems illustrates the complexity and obstacles that developers and planners face when it comes to grid integration. It is the first step in ensuring that the integration of a solar installation does not negatively impact the public grid and always precedes any PV construction work. Early contact with the grid operator is essential to avoid delays. A negative NVP can severely hinder or even completely slow down the realization of a project, especially if the grid expansion incurs high costs. This is currently one of the biggest obstacles.

The high number of completed PV systems that have not yet received grid operator approval is also particularly worrying. This second bottleneck leads to a standstill in investment and a potential risk for the energy transition. It is clear that measures must be taken to minimize bottlenecks and delays and to maintain the attractiveness of photovoltaic investments.

The energy transition requires a joint effort by all stakeholders to enable the transition to a low-carbon future. Grid compatibility assessment is one of the key components that will make it possible to integrate large-scale PV systems efficiently and responsibly, paving the way for a sustainable energy future.