Knowledge · Grid connection · 06/11/2026 · StromWert
Sizing grid connection capacity before you file the connection request
The capacity you state in the connection request determines the voltage level, the construction cost contribution and the grid reinforcement required. Here is how to size it from your load profile and planned loads, neither too tight nor too generous.
Why the figure in the request matters so much
In the connection request you tell the grid operator how much capacity to reserve at your connection point. That figure decides which voltage level you connect to, whether existing cables and transformers are sufficient and how large the construction cost contribution will be. The route from request to commissioning is described on our grid connection page; this article is about the figure itself.
The reserved capacity is not the same as the capacity you pay network charges for. For connections with power metering, the network charge consists of an annual capacity price multiplied by the annual peak demand, plus an energy price for the kilowatt hours drawn (Section 17(2) StromNEV, the German network charges ordinance). In practice the annual peak is the highest 15-minute value recorded by the power meter. A single peak in the year therefore sets the capacity part of your network charge.
Sized too tight, the connection will not cover the next expansion stage, and a new request can take months to assess again. Sized too generously, you usually pay a higher construction cost contribution for capacity you never use, and you may end up one voltage level higher than necessary. The threshold for a medium-voltage connection is set out in the grid operator’s technical connection conditions.
Step 1: Analyse your current load profile
The basis is the load profile of your existing connection: the 15-minute values of the power meter over at least twelve months. You can get it from your metering point operator or your electricity supplier, and many grid operators show it in their customer portal. Twelve months, because heating, cooling and production run differently through the seasons.
01
Find the peak
The highest 15-minute value of the year is your current annual peak demand. It also appears on the network charge invoice.
02
Explain the peaks
Check when the highest ten to twenty quarter hours occurred and what was running at the time: large machines starting up, shift start, chillers in summer, several vehicles charging at once. Often it is only a few hours a year.
03
Read the base load
The demand that never drops away at night or at weekends shows what runs permanently.
04
Build a load duration curve
Sort all quarter hours of the year in descending order. The curve shows in how many hours a given demand is really needed, and therefore how much a battery can shave off.
Step 2: Add new loads correctly
On top of today’s annual peak come the loads you plan for the coming years. What matters is not the sum of the rating plates but how much of it runs at the same time. This diversity factor varies widely between types of load.
Your own rooftop PV lowers the demand on sunny days, but not the peak on a dull winter evening. Do not deduct it from the demand capacity. It determines the export capacity, which you state separately in the same request.
AI servers and cooling
GPU servers run close to full load for hours during training, and the cooling runs with them. As a rule, plan for the full electrical load of IT and cooling, without a diversity discount. How we build the supply for an on-prem data centre is explained on its own page.
Charging points
Charging equipment must be notified to the grid operator before commissioning. At low voltage, a combined rating above 12 kVA needs the operator’s prior consent, and the operator must respond within two months (Section 19(2) NAV). With load management the charging points share a fixed limit, and that limit is what counts. More on EV charging infrastructure.
Heat and fleet
Electrifying process heat, space heating or vehicles moves load from gas and diesel onto the grid. This load often falls in the winter months and can coincide with today’s peaks.
Plan in stages and state the stages with a timeline in the request. The grid operator can then check whether the first stage is possible right away and the next ones follow with grid reinforcement.
Step 3: Shave the peak with a battery
A commercial battery absorbs the peaks in the load profile: it discharges as soon as the demand reaches a set limit and recharges when the load is low. This lets you run a higher load on the existing connection or keep the capacity in the new request smaller. How this works in operation is shown under peak shaving.
For sizing this means two things. First, a battery works in two directions: it draws power when charging and exports when it discharges to the grid. Both belong in the request. Second, the controller must prevent charging itself from creating a new peak, for example when the battery and the charging hub both draw power at night.
The battery is subject to the same grid connection rules. In 2025 the Federal Court of Justice (Bundesgerichtshof) ruled that grid operators may charge a construction cost contribution for battery storage under the capacity price model (decision of 15 July 2025, EnVR 1/24). The connection priority that renewable generation enjoys does not apply against storage (Section 17(2a) EnWG). Which size suits your site is covered on our commercial battery storage page.
Worked example: plant with charging hub, servers and battery
A simplified example with assumed values, not a design for a real site. It shows the order of the calculation.
| Item | Capacity | Assumption |
|---|---|---|
| Current annual peak demand | 1,200 kW | from the load profile of the last twelve months |
| New production line | + 300 kW | 375 kW connected load, diversity factor 0.8 |
| Charging hub with load management | + 200 kW | fixed limit of the load management, not the sum of the charging points |
| AI servers with cooling | + 250 kW | IT and cooling without discount |
| Total without battery | 1,950 kW | demand capacity that would have to be reserved without a battery |
| Battery shaves peaks | − 350 kW | only if the load duration curve shows that the peaks are short |
| Demand capacity in the request | 1,600 kW | plus the next expansion stage with a timeline |
| Export capacity in the request | 500 kW | rooftop PV; the battery only discharges behind the meter |
The figures are an example. For your site we calculate with your load profile and your grid operator’s technical connection conditions.
When the grid operator cannot release the full capacity
Grid operators must connect final consumers, charging points, generators and storage on appropriate, non-discriminatory and transparent terms (Section 17(1) EnWG, the German Energy Industry Act). They may refuse a connection only to the extent that it is not possible or not reasonable for operational, economic or technical reasons, and they must give the reasons in text form. If capacity is lacking, you can ask for the reasons to include the reinforcement measures required and their cost (Section 17(2) EnWG).
Grid operators can also offer a flexible connection agreement (Section 17(2b) EnWG). Under it they may require a static or dynamic limit on the import or export capacity. The agreement must set out the level and periods of the limit, its duration, the technical requirements and liability for exceeding it. For generators, Section 8a EEG contains its own rule on limiting export.
For sizing this is an opportunity: if your load profile tells you how much capacity you need in which hours, you can accept a temporary limit and cover it with a battery or load management.
What goes into the connection request
The exact forms and documents your grid operator requires are set out in its technical connection conditions. As a rule, the request includes:
- Demand and export capacity: separately, in kilowatts, for each expansion stage.
- Timeline: when each stage is to go into operation.
- Load profile: the 15-minute values of the last twelve months, if a connection already exists.
- Loads, generators and storage: with capacity, mode of operation and planned load management.
- Site plan: the plot, the existing connection and the preferred location of the transfer or transformer station.
- Contact person: who answers the grid operator’s technical questions.
Outlook: what the grid package is set to change
In July 2026 the federal government adopted a draft act to synchronise the build-out of installations with grid expansion, known as the grid package (Bundestag printed paper 21/7866). As of 6 November 2026 it has not been passed. Everything in this section is planned according to the government draft and may still change in parliament.
Distribution system operators are to introduce a uniform procedure for reserving connection capacity for connections from 135 kW: in time-limited stages, tied to project progress and possibly subject to a fee (Section 17f EnWG draft). Grid operators are to be able to reduce reserved capacity that has gone unused for years and is likely to remain unnecessary (Section 17(1a) EnWG draft). Maps of available connection capacity and status updates on requests within two months are also planned.
For sizing this would mean: a reserve that is never used could be lost again, and the reservation itself could carry a cost. Capacity that is justified by the load profile and requested in stages with a timeline remains the reliable route.
Sources
- Section 17 EnWG, grid connection (German)
- Section 17 StromNEV, calculation of network charges (German)
- Section 19 NAV, operation of installations and charging equipment (German)
- Section 8a EEG, limiting export capacity (German)
- Goerg: Federal Court of Justice approves construction cost contribution for batteries, EnVR 1/24 (German)
- Government draft of the grid package, printed paper 21/7866 (German)
- CMS: grid package 2026, new rules for grid connections planned (German)
- Goerg: federal government adopts grid package (German)
Frequently asked questions on connection capacity
How is the connection capacity of an AI data centre sized before the connection request is filed?
From the electrical load of the IT at full build-out plus cooling and auxiliary systems, as a rule without a diversity discount, because GPU servers run close to full load for long periods during training. If the data centre sits on a factory site, today’s annual peak from the load profile is added. State the expansion stages with a timeline in the request.
What connection capacity do I need for my commercial battery?
A battery needs capacity in two directions: import for charging and export if it discharges to the grid. If it only works behind the meter and shaves peaks, it can reduce the demand capacity the site needs. The controller must then prevent charging from creating a new peak.
Where do I get my load profile?
From your metering point operator or your electricity supplier, as 15-minute values for connections with power metering. Many grid operators also show it in their customer portal. Ask for at least twelve months.
Can the grid operator refuse my connection?
Only to the extent that the connection is not possible or not reasonable for operational, economic or technical reasons, and with reasons given in text form (Section 17(2) EnWG). If capacity is lacking, you can ask for the reinforcement measures required and their cost. For this the operator may charge at most half of its costs, provided it pointed this out beforehand.
What happens if I need more capacity later?
You notify the grid operator of a higher reserved capacity; at low voltage this is expressly required (Section 19(2) NAV). The operator then checks again whether the grid can carry the additional load. That is why it pays to state the expansion stages in the first request.
As of 6 November 2026. This article is not legal advice and not a design for a specific site. For the grid package, the government draft applies.