Backup operations permitted in Hungary from 2025

In 2025, a significant change came into force regarding the regulation of domestic solar panel systems in Hungary: grid-connected systems with backup/EPS (Emergency Power Supply) functionality are now officially permitted.
This is a particular improvement for residents. Previously, in the event of a power outage, household-sized solar power plants (HMKEs) would automatically shut down. There was no possibility for our own solar panel system to provide energy even then – regardless of whether the sun was shining or if we had a battery.
The new regulation changes this: with appropriate technical design, it is now possible for a solar panel system to operate even during a power outage – meaning it can switch the household to island mode.

In this article, we will present:

• what types of systems exist (grid-tied, off-grid, hybrid);
• what backup/EPS functionality means from a technical and legal perspective;
• how the regulations changed from 2025;
• and what to pay attention to during planning and implementation.

We will also discuss the benefits this brings to households, and briefly touch upon the impacts on industrial systems.

Types of Solar Panel Systems – A Brief Overview

To understand the essence of the backup/EPS function, it's worth first reviewing how different types of solar panel systems work. We distinguish three main types – based on their connection to the public grid:

Grid-tied system:

This is the most common type.

The solar panels and the inverter are continuously connected to the utility power grid. The energy produced is first consumed by the household, and any surplus – if permitted – can be fed back into the grid.

Important limitation: in the event of a power outage, such a system automatically shuts down. Since there is no grid reference voltage, the inverter does not continue to operate – and for safety reasons, it should not. This is to prevent feedback into the grid when technicians might be working on it.

Off-grid system:

This type is completely independent of the public grid.

The solar panels, inverter, and battery together form a closed, standalone system – providing power to all consumers in the household. A grid power outage does not affect such a system at all.

This solution is primarily characteristic of locations where there is no available electrical grid, or where the owner deliberately strives for complete energy independence.
Its disadvantage is that it requires significant battery capacity to maintain continuous supply – especially during longer cloudy periods or winter months.

Hybrid system:

This solution is a combination of the two.

A hybrid system connects to the grid but also has a battery and is capable of automatically switching to off-grid mode in the event of a power outage – provided it also has backup/EPS functionality.

Under normal circumstances, the system operates in conjunction with the grid: it consumes what it produces, feeds any surplus back, and draws from the grid if necessary.

In the event of a power outage, however, it can continue to operate as an independent island, disconnecting itself from the grid – this is called backup or EPS operation.

Many interested parties have sought this solution in recent years, but it has not been officially permitted in Hungary until now. However, this has now changed – and the next part of the article is about this.

What is backup/EPS functionality and how does it work?

The essence of the backup – or also known as EPS (Emergency Power Supply) – function is that the solar panel system is able to provide power even when there is no grid voltage. In other words: if there is a power outage, the system does not shut down completely, but continues to operate and supply energy to certain consumers – or even the entire household.

Of course, a battery alone is not enough for this. The system must be able to "disconnect" from the public grid and switch to island mode. This is ensured by a separate output – the so-called backup or EPS output – and an associated automatic control unit. As soon as the system detects a power outage, the inverter switches to island mode and only supplies energy to the internal network of the house. The connection to the external grid is interrupted, thus eliminating the danger of back-feeding – which in such a case would not only be illegal but also life-threatening.

An important difference is that most traditional solar panel systems still shut down during a power outage, even if they have a battery. In this case, the inverter "does not know" what to do – because there is no built-in backup function and it is not able to disconnect from the grid. Real backup operation, however, works like an uninterruptible power supply: it switches over automatically within milliseconds, and the power supply continues seamlessly. Most household appliances – such as lighting or the internet – do not even notice this switch.

However, the system can only provide power as long as there is a source. If the sun is shining, the solar panels generate power, but if it's cloudy or nighttime, the battery capacity sets the limit. Therefore, proper sizing is crucial: it is necessary to know how long and which devices we want to supply. A smaller storage might be sufficient for a shorter outage, but if the goal is to keep, for example, the refrigerator, lighting, and heating control operating for hours, then greater capacity will be needed. Large consumers – such as the oven or washing machine – are usually not connected to the backup branch in such cases, or only with conscious planning.

Why was backup mode not permitted in Hungary until now?

Behind this were several, primarily safety and legal reasons – which long prevented the widespread adoption of backup technology.

Touch protection and life safety

The most important concern was the risk of accidents caused by back-feeding. If the public grid becomes de-energized due to maintenance or a fault, no domestic power plant – not even a small solar panel system – can feed power back into it. Unexpected back-feeding would pose a direct threat to the lives of technicians working on the grid, who expect the wires to be de-energized during their work.

Therefore, it was strictly mandated that grid-connected inverters automatically shut down if the grid disappears. International standards, such as the "anti-islanding" protection, serve precisely this purpose: inverters must be able to detect a grid outage and immediately interrupt production.

Reconnection is also regulated

When the grid is restored, reconnection cannot happen in any arbitrary way either. Providers often stipulate delayed reconnection – typically with a delay of 1-5 minutes – so that many individual solar panel systems do not all start feeding back at once, which could lead to sudden voltage fluctuations. If a system operates in island mode but does not reconnect to the grid synchronously, it can cause serious frequency and voltage problems. To avoid these, the permitting of hybrid or backup-mode systems was previously excluded.

Regulatory shortcomings and utility rejection:

Even if the technology was ready – several manufacturers, such as Fronius or Solax, had been offering inverters with backup outputs for years – the official regulations did not cover their handling. It was unclear under what technical and legal conditions a system could be both grid-connected and capable of island operation simultaneously.
Therefore, utilities consistently rejected the installation of such systems. Their connection regulations clearly stated that grid-connected solar panel systems with backup functionality were not permitted. Users who nevertheless insisted on power outage protection could only consider "workarounds" – for example, through separate socket outlets belonging to certain inverters, such as the Fronius PV Point. However, these could only supply power to a few smaller devices (e.g., lamps, routers) and were not integrated into the house's entire network – so they cannot truly be considered real backup solutions.

The 2025 regulatory change: what is permitted and what has changed?

One of the most significant novelties is that Act LXXXVI of 2007 – more commonly known as the Electricity Act – officially introduced the concept of "household electricity storage." According to this, any battery-powered device with a capacity of at least 2 kWh, which can be operated independently and recharged, can now be recognized as part of the electricity system. This means that the role of home battery storage units – not only technically but also legally – has been acknowledged.

Furthermore, the regulation clarified the technical requirements for "mixed-mode" (i.e., systems capable of both grid-connected and island operation) systems. Annex 6/B of the network regulations, for example, describes in detail the additional requirements such a system must meet. These include, for instance, the presence of an automatic disconnecting device, the safe design of island operation, and the necessary protective functions.

In practice, this means that from 2025, service providers can now approve household solar panel systems that, in addition to traditional operation, can also switch to island mode in the event of a power outage. However, this is not an automatic option for all systems. Only those systems that fully comply with the relevant technical and safety regulations can receive permission with backup functionality. During implementation, therefore, it is not enough to simply install the hardware: the prescribed standards, the establishment of proper protection, and consultation and approval with the service provider must also be taken into account.

This change is particularly important for the public, as it significantly increases supply security. During a regional or national power outage, the house does not have to be plunged into complete darkness – if there is a battery and the system is prepared for backup operation, at least essential devices (such as the refrigerator, lighting, heating control) can continue to function uninterrupted.

It is worth mentioning that the regulatory direction aims to encourage domestic energy storage and self-consumption. This is also reinforced by the fact that from 2024, gross billing replaced the previous net metering model – meaning that feeding back energy is financially less worthwhile than what we use locally. A battery-combined backup system also offers an advantage in this situation: it helps in utilizing one's own production within the house and also acts as emergency protection.

Permitting and Installation Conditions in Practice

The installation of a solar panel system with backup/EPS functionality presents challenges not only from a technical but also from an administrative perspective. Many people are in a situation where they already have solar panels and possibly a battery, but later want to expand the system with an off-grid capable solution. In such cases, a new notification must be submitted to the service provider, as if it were a new application.

The service provider typically requests the following:

• New application: it must be indicated that the system will also be capable of backup/power outage operation.
• Modified connection plan: it must include the technical solution, details of the EPS connection, wiring diagrams, and equipment types.
• New completion report: after implementation, it must be certified that everything was carried out according to the approved plan.
  

These steps are the same as for establishing a new HMKE, only now the documentation is expanded due to the backup function.

When planning a new system, it is advisable to indicate the backup requirement from the outset. This way, the designer will already work with inverters and accessories that are on the list of approved devices and comply with relevant standards (e.g., EN 50549, anti-islanding certification, etc.).

It is important to involve an expert, because:

• Grid protection settings (e.g., VDE AR-N 4105) require precision.
• The professional installation of the backup switch (e.g., EPS relay) is crucial.
• A bidirectional meter may also be required.
  

The heart of the backup system is the automatic transfer switch unit, which disconnects the household from the utility grid in the event of a power outage. The system must operate so that under normal circumstances, the entire house runs on the utility grid, but in the event of a power outage, it directs the power supply either to a separate backup circuit (for essential loads) or even to the entire house – but never feeds back into the grid.

Hybrid inverters and backup solutions

More and more manufacturers offer hybrid inverters with backup functionality, but it is important to distinguish: not all hybrid inverters can automatically switch to island mode. This requires the appropriate function and often an additional device.

• Deye inverters: come with factory-integrated backup functionality. No separate EPS box is required; the inverter itself can handle grid outages.
• SolaX and Huawei inverters: require a separate add-on module (EPS or Backup Box) that provides automatic transfer switching. These contain two contactors: one disconnects the grid, the other connects the house's internal network to the inverter.
• Huawei Backup Box: available in single- and three-phase versions. Provides fast transfer, capable of supplying power to an entire household.
• SolaX EPS Box: a separately sold unit, without which the inverter cannot operate in island mode. After installation, it forms a full-fledged backup system.

The goal in all cases is the same: automatic and safe disconnection of the household, followed by power supply to internal consumers using the battery and solar panels. The transfer time is typically a few hundredths of a second – so a router or computer will not necessarily restart either.

What to consider during planning?

• Backup operation does not mean that all consumers can operate without limit.
• The inverter's power and battery capacity determine what and for how long can be operated during a power outage.
• It is advisable to connect only the most important devices to the backup circuit: lighting, refrigerator, heating circulator, router, security technology.
• High-consumption devices (oven, air conditioning, car charger) are generally not advisable to use in backup mode – unless the system is sized for it.
  

Installation professionals help calculate the required battery capacity: this requires knowing the power of the devices covered by the backup and the expected operating time. Based on this, the necessary kWh capacity can be determined – whether it's for a few hours or a full day of bridging.

Summary

A solar panel system with a battery alone does not provide off-grid capability – this requires the installation of a backup or EPS function. In Hungary, this was not previously permitted by service providers and regulations, due to safety considerations. However, from 2025, this has changed: hybrid solar panel systems (grid-connected but also operating during power outages) have officially become permissible.
In practice, this means that a well-designed and implemented backup system can bridge power outages without having to give up the benefits of grid connection. For users, this means greater independence, security, and more efficient energy use.
However, it is important that the implementation is professional. This is the only way to ensure that the system complies with both relevant standards and service provider expectations. It is advisable to entrust the work to an experienced design and installation team.
Thus, all stakeholders can benefit from the regulatory change: residents, grid operators, and even industrial consumers. Systems equipped with backup functionality make the country's energy system more stable and bring us closer to a sustainable, renewable-based future.