In the past, the grid connection was a formality. An application to the grid operator, a meter cabinet, done.
Those days are over.
Today almost every new building has a heat pump. Add wallboxes, a PV system on the roof and often a battery storage unit in the basement. Each of these devices changes the building’s load balance. And each brings its own rules.
Anyone who only learns those rules at commissioning pays for it — with meter-cabinet alterations, variations and weeks the construction programme cannot spare.
In this article I show which three sets of rules shape the grid connection today — and how good electrical design accounts for them from the start.
Three sets of rules, one meter cabinet
At a building’s grid connection, three sets of rules meet:
- VDE-AR-N 4100 (TAR Niederspannung): It governs the connection of customer installations to the low-voltage network. That includes the service connection, meter cabinet and load registration.
- VDE-AR-N 4105: It governs generating plants and storage on the low-voltage network — so PV systems, battery storage and their grid and plant protection functions.
- § 14a EnWG: It governs controllable consumption devices — heat pumps, private wallboxes, air-conditioning units and storage above 4.2 kW.
On top come the Technischen Anschlussbedingungen (TAB, the grid operator’s technical connection conditions). They flesh out the application rules and differ in detail from one network area to another.
The point where all of this comes together is the meter cabinet. That is exactly where most surprises arise in practice.
The TAR Niederspannung has been revised
Since 2026, VDE-AR-N 4100 has been available in a fully revised edition. A further amendment (A1) is already in draft. It is intended to simplify the roll-out of metering and control technology — for example by preparing the meter cabinet digitally.
The direction is clear: the meter cabinet becomes the interface between building and grid. It must leave room for smart metering systems, control boxes and communication with the grid operator.
For design that means: do not size the meter cabinet to the millimetre. Reserves for metering, control technology and later extensions belong in the detailed design from day one. Altering it after completion costs many times more.
§ 14a EnWG: control instead of refuse
Since 1 January 2024, § 14a EnWG has applied to new controllable consumption devices. The principle is simple. The grid operator may not refuse the connection because of network congestion. In return, it may dim the devices if overload is imminent.
Dimming is not to zero. With individual control, a minimum power of 4.2 kW per device remains. With an energy management system (EMS), a shared limit applies across several devices. Ordinary household electricity is not affected.
In return, the network charge falls. The operator chooses between a flat reduction (module 1), a reduced energy price with a separate meter (module 2), or additionally a time-variable network charge (module 3).
And this is where design gets interesting. Module choice has consequences for the meter cabinet. Module 2 needs its own meter for the controllable consumption device. Anyone who decides that only after the cabinet is installed will have to rebuild.
Five questions that should be settled before detailed design
From my experience in installation, design and client representation, I clarify these five questions as early as possible — ideally already in preliminary design (LPH 2 / HOAI work stage 2):
- Which loads and generators will the building have? Heat pump, wallboxes, PV system, storage — today and in ten years.
- What does the load balance look like? With realistic diversity factors, not blanket values.
- Individual control or energy management system? An EMS can distribute available power intelligently during a dimming event. But it has to be designed, wired and integrated into the building automation.
- Which module under § 14a should apply? The answer determines how many meter positions are needed.
- What do the grid operator’s TAB require in concrete terms? A short check beforehand saves arguments at registration.
None of these questions is new. What is new is that they now arise together in almost every project.
Why this topic belongs with a designer who knows the site
On paper a lot looks simple. An extra meter here, a control cable there.
On site it looks different. The meter cabinet is already ordered. The wall is too narrow. The control cable to the heat pump is missing because it was never on a drawing.
As an electrician I built meter cabinets and distribution boards myself. As a project engineer I designed grid connections to TAB and VDE-AR-N 4100. And as a client representative I have seen what it costs when an interface is clarified too late.
That is why I do not treat the grid connection as the last step — but as one of the first.
Conclusion
In 2026 the grid connection is no longer a form. It is a design task. The new TAR Niederspannung, VDE-AR-N 4105 and § 14a EnWG interlock. Anyone who thinks them through early saves alterations, variations and time.
Anyone who ignores them will meet them at commissioning.
Planning a building with a heat pump, wallboxes or a PV system and want the grid connection set up correctly from the start? Let’s talk.
Note: This article gives an overview and does not replace project-specific design. The current editions of the rules and the TAB of the responsible grid operator are authoritative.
Sources: VDE FNN, TAR Niederspannung · 42watt, § 14a EnWG