In recent years, residential and commercial & industrial (C&I) solar installations have expanded rapidly across Europe. Distributed PV has become deeply integrated into low-voltage distribution networks and now plays an important role in the power supply.

When PV penetration was still relatively low, the inverter had a straightforward job: generate power reliably and disconnect from the grid immediately when an abnormal condition was detected, prioritizing equipment protection.

But as PV penetration has increased significantly, the way the grid operates has changed. If a minor disturbance or fault occurs, large numbers of inverters disconnect from the grid at the same time. What starts as a small grid disturbance can then be amplified, potentially leading to widespread power outages.

Against this backdrop, European grid-connection requirements are undergoing a major shift. Inverters are no longer expected to simply disconnect for self-protection. Instead, distributed PV systems are increasingly required to actively support the grid by withstanding disturbances and helping maintain voltage and frequency stability.

Germany’s new VDE-AR-N 4105:2026-03, which officially took effect in March 2026, has become a key reference point for this broader European grid-connection upgrade. Among the changes, the requirements for PSTI (Power System Transient Immunity) have been significantly tightened, making transient immunity a critical market-access requirement for PV and energy storage equipment entering Europe.

This article breaks down Germany’s key new requirements in plain language. It also provides an overview of special grid-connection requirements for Mediterranean islands, EU-wide standards, and Italy’s market policies, offering a practical reference for EPCs, pre-sales engineers, procurement teams, and project managers working on European market expansion.

1. Germany’s 2026 Grid-Connection Rules: Strengthening the Existing Framework

VDE-AR-N 4105 is a benchmark standard for low-voltage grid connection in Europe. It applies to grid-connected PV and energy storage equipment rated up to 500 kW. The 2026 edition officially replaces the 2018 version and is expected to have a strong influence on low-voltage grid-connection compliance across Europe.

To put the previous version simply, its focus was on safety rather than grid support.

The previous standard established a basic safety framework, including rapid disconnection in the event of leakage faults and short-duration voltage ride-through during faults. These requirements helped reduce unnecessary equipment disconnections. However, the rules were relatively less demanding when it came to minor grid disturbances, single-phase faults, and equipment immunity to interference. Certain energy storage systems could also benefit from specific testing exemptions.

The 2026 edition follows a clear direction: as PV penetration continues to rise, inverters can no longer rely primarily on passive protection and disconnect too easily. They need stronger disturbance immunity and active grid-support capabilities to operate reliably under more complex grid conditions.

The update does not overturn the existing safety requirements. Instead, it addresses specific gaps in grid operation, with six key changes:

1. Energy Storage Is No Longer Treated Differently

Previously, AC-coupled energy storage equipment could be exempt from certain leakage-current tests. Under the 2026 requirements, these exemptions have been removed.

Energy storage equipment must now follow the same leakage protection testing requirements as PV equipment, helping address potential safety risks to both people and the grid.

2. New Voltage Support Requirements for Single-Phase Faults

In real-world power grids, faults are more commonly associated with single-phase conditions rather than ideal three-phase symmetrical faults.

The previous standard focused on three-phase symmetrical fault scenarios. The new version introduces adaptive reactive-power voltage support during single-phase faults.

When a single-phase short circuit occurs, the inverter is required to actively provide reactive power to help stabilize the voltage on the remaining two phases, reducing the risk of abnormal voltage rises that could damage other grid-connected equipment.

3. Voltage Support Can No Longer Rely on Simply Reducing Power Output

Some equipment previously addressed insufficient reactive-power capacity by reducing active power output and sacrificing energy yield to help stabilize grid voltage.

The new standard explicitly rules out this approach.

Within the normal voltage range, equipment must rely on its own reactive-power capacity for voltage regulation. This places greater demands on inverter hardware and its ability to provide grid support.

4. PSTI Requirements Tightened Significantly

This is one of the most important changes in the 2026 update.

In everyday grid operation, brief voltage spikes, small fluctuations, and short-duration pulse disturbances can occur frequently. Inverters with limited disturbance immunity may respond by disconnecting unnecessarily.

The new standard significantly tightens the PSTI transient immunity test waveforms and acceptance thresholds. Inverters are expected to withstand minor grid disturbances while maintaining stable grid connection and avoiding nuisance tripping.

In simple terms, the new requirement is:

“Small grid fluctuations should not cause equipment to disconnect from the grid.”

The goal is to prevent a minor local disturbance from triggering large-scale simultaneous disconnections and potentially contributing to widespread outages.

Many older models and legacy firmware versions may not meet the new requirements and will need to undergo type testing again before they can comply with the updated standard.

5. Higher Compliance Thresholds for Microinverters

The new rules also raise the regulatory threshold for microinverters.

Microinverters rated 800 VA and above are now included in the mandatory grid-connection testing scope, removing the previous compliance flexibility for certain low-power devices.

6. Equipment Registration Is Now Mandatory

Germany’s ZEREZ equipment registration system, which was previously encouraged, has become mandatory.

All grid-connected equipment must be registered and traceable throughout its lifecycle. Equipment that has not been registered or does not have the required registration records will not be able to pass grid-connection acceptance.

Key Market-Access Requirements

The new standard represents a mandatory compliance threshold for equipment entering Germany’s and Europe’s low-voltage PV markets. Product certification alone is no longer sufficient.

Manufacturers targeting the European market should pay particular attention to two areas:

First, upgrade both hardware and software to meet the tightened PSTI transient immunity requirements. Older equipment should be optimized and undergo the necessary type testing in advance to reduce market-access risks.

Second, complete mandatory ZEREZ registration to ensure full lifecycle traceability and compliance.

At the same time, energy storage equipment and microinverters rated 800 VA and above are no longer eligible for the relevant testing exemptions. They must complete the required compliance updates before entering the European market.