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Glossary · Energy industry & energy transition

Construction cost contribution (Baukostenzuschuss)

Construction cost contribution grid connection grid fee distribution grid Connection costs electricity grid

A construction cost contribution (Baukostenzuschuss, BKZ) is a one-off sum of money that a connection user pays to the grid operator. It falls due when a new grid connection is established or when the ordered capacity of an existing connection is increased. In this way, the connection user contributes to the costs of building or reinforcing the grid facilities that they share with others, such as local network lines or transformer stations. What matters is not the quantity of electricity supplied in kilowatt hours. What counts is the capacity that the grid operator must keep permanently available at the connection. The BKZ therefore belongs to the costs of access to the grid and not to the ongoing electricity costs. All statements in this entry refer to Germany and the situation as of November 2026.

Basis of assessment: capacity to be kept available

The key variable is the connection capacity, that is, the maximum capacity that may be drawn at the grid connection point. It is stated in kilowatts or megawatts. The reason lies in grid planning: lines, transformers and switchgear are designed according to the capacity that can flow simultaneously, not according to annual volume. An example: a business that rarely but briefly draws 500 kW loads the grid more heavily at that moment than a household that consumes a lot of electricity over the year but never draws more than a few kilowatts at the same time. For the design, simultaneity is therefore decisive. It describes how likely it is that many consumers request high capacity at the same time. For low-voltage connections, the ordinance expressly requires this diversity of capacity demands to be taken into account.

Distinction from grid connection costs and the grid charge

The BKZ must be kept separate from the grid connection costs. These pay for the specific link between the customer's installation and the grid, for example the service connection, that is, the cable, the service connection box and civil engineering work along the connection route. The BKZ, by contrast, covers a share of the shared, upstream infrastructure. In the low-voltage level, both items must be calculated separately and shown individually on the invoice.

The BKZ also differs from the grid charge. Grid charges are levied continuously through energy and capacity prices and finance the operation, maintenance and expansion of the grids. The BKZ, by contrast, arises only on a specific occasion, namely with a new connection or a significant increase in capacity. It is thus an entry payment or a payment for an extension.

Legal framework at low-voltage level

For connections to the low-voltage grid, that is, typically households and smaller businesses, section 11 of the Low-Voltage Connection Ordinance (Niederspannungsanschlussverordnung, NAV) governs the BKZ. The most important requirements:

  • Purpose: The BKZ covers only part of the costs that are necessary, with economically efficient operation, to build or reinforce the local distribution facilities, including transformer stations. The facilities must be attributable to the supply area of the connection.

  • Upper limit: The BKZ may cover no more than 50 percent of these costs. The rest is financed by all grid users through the grid charges.

  • Allocation key: The connection user's share depends on the ratio of the capacity they require to be kept available to the total capacity that the facilities can provide. Grid operators may also calculate it as a flat rate, on the basis of the average costs of comparable cases.

  • Exemption threshold: A BKZ may be demanded only for the part of the capacity requirement that exceeds 30 kW. A usual service connection of up to 30 kW therefore remains free of charge. Even at 40 kW, payment is made only for the excess 10 kW.

  • Additional demand: If the connection user later increases their capacity requirement considerably above the originally calculated value, the grid operator may demand a further BKZ.

This is becoming more important with electrification. A heat pump, several wallboxes and an instantaneous water heater can together exceed the 30 kW threshold if they are allowed to run at the same time. Load management limits the simultaneous capacity. This can reduce the ordered capacity and, under certain circumstances, the BKZ.

Grid levels above low voltage

For connections at medium and high voltage, there is no ordinance like the NAV. Here, the connection conditions must be reasonable and non-discriminatory under section 17 of the Energy Industry Act (Energiewirtschaftsgesetz, EnWG). How grid operators proceed in this respect is shaped significantly by a position paper of the Federal Network Agency (Bundesnetzagentur). The first version dates from 2009 (ref. BK6p-06-003). The paper describes the so-called capacity price model: in simplified terms, the BKZ results from the capacity prices of the respective grid level and the ordered capacity. It thus becomes higher the more capacity is ordered. In the view of the Federal Court of Justice (Bundesgerichtshof), the BKZ thereby has two functions. It provides guidance and steering, for example in sizing and site selection. In addition, it contributes to financing the distribution grid. Grid operators may orient themselves on these guidelines, but they retain their own margin of discretion in doing so.

Battery storage

Whether grid-connected storage facilities must pay a BKZ was disputed for a long time. The Federal Court of Justice confirmed this by decision of 15 July 2025 (EnVR 1/24) for a purely grid-connected battery storage system. A BKZ calculated under the capacity price model is permissible. Treating storage like other final consumers is not discriminatory, insofar as they use the grid through withdrawals. The court acknowledged that storage facilities do not consume the electricity but feed it back in with a time delay and can also act in a grid-serving way. However, the operator's willingness to relieve the grid was not decisive for the decision. The Federal Network Agency sees no ground for a discount in the storage function alone. In practice, what matters is therefore the maximum withdrawal capacity at the connection, not the planned mode of operation.

Generation installations

A different logic applies to installations under the Renewable Energy Sources Act (EEG 2023), such as photovoltaic installations or wind farms. Under section 16 EEG, the installation operator bears the necessary costs of the connection up to the connection point. Under section 17 EEG, the grid operator bears the costs of optimisation, reinforcement and expansion of the grid. Under current law, there is therefore no BKZ for feed-in from such installations. The term should not be used for every payment in connection with a feed-in installation.

This could change. In the procedure on the new grid charge system, the Federal Network Agency published guiding points in February 2026. In them, it also advocates a one-off BKZ for feed-in operators, assessed on the basis of the chosen connection capacity. So far, this is only a proposal and not applicable law. According to trade reports, the BKZ is to be specifically regulated only in follow-up procedures.

Cost allocation and incentives

At its core, the BKZ is about the question of who bears the costs of grid expansion. If they are spread entirely across everyone through grid charges, individuals can order large capacities without feeling the follow-on costs. This favours oversized connection requests, for example for charging parks, data centres or commercial areas. If, on the other hand, the costs are attributed heavily to the individual, this can slow down investments in electrification that make sense for the economy as a whole. The upper limit of 50 percent in the NAV is such a compromise. For distribution system operators, the BKZ also links connection requests with the available grid capacity. A connection with high capacity can be unproblematic where the grid has reserves. Elsewhere, the same connection can trigger considerable grid reinforcement.

Flexibility plays a growing role here. Anyone who can control or limit their load needs less guaranteed capacity and thereby reduces the need for immediate grid expansion. How flexible grid connection agreements are supposed to interact with the BKZ in future is, as of November 2026, still open from a regulatory point of view.

Classification

The BKZ is neither a technical installation nor a component of the electricity price. It is a cost rule at the interface between the individual connection and the shared grid infrastructure. A high BKZ can indicate scarce local grid capacity, but can also be the result of flat-rate calculation rules. A low or absent BKZ does not mean that no costs arise. They are merely distributed differently, namely through the grid charges of all users. Anyone who uses the term precisely distinguishes between connection costs, grid reinforcement, the ongoing grid charge and actual electricity consumption.

Sources

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Edited by eCMS on 11.11.2026 15:19

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