Expanding a PV System: Smart Options

If the need for electricity increases due to new devices, a new family member or an electric car, the question of expanding the PV system quickly arises. Fortunately, existing systems can be flexibly adapted. Roof, facade, garage or garden – there are many areas that can be used. But in addition to the modules, inverters, statics and EEG rules also have to be taken into account. Those who plan the expansion wisely will secure more independence in the long term and take another step towards the energy transition.

PV system expansion: key facts at a glance

• Additional modules are the most common extension, but only make sense if there is sufficient roof space and statics.
• Facades, terraces, garages, carports, fences and balcony solar systems offer alternatives.
• Inverters and meters must also be checked for compatibility when expanding.
• In the case of the EEG remuneration, the expansion is considered a new installation with current remuneration rates.
• Storage solutions can replace an expansion or usefully supplement it.

Can an existing PV system be expanded easily?

Yes, an extension is usually possible, but requires checking the roof statics, inverter, compensation and registration with authorities.

Installing additional solar panels on the roof

The most obvious way to expand a photovoltaic system is to retrofit additional solar modules on the roof of the house. The prerequisite is that there is still enough unused space there. The load-bearing capacity of the roof is important: it must withstand at least 30 kilograms per square meter to carry the additional load.

Only if this condition is met can an extension be considered. The compatibility of the modules is also crucial. Although it is enough if the new modules are technically compatible, identical models deliver the best results. You should also check the shading, because new modules must be able to work under comparable conditions. If they are shaded by trees or neighboring houses, the performance drops noticeably. It should also be noted that the additional number of modules changes the voltage in the string, which affects the inverter.

Therefore, professional planning is mandatory. The existing cabling and fuses must also be checked. Another point: The effort is only worth it if the site conditions are at least good. An extension on the roof offers clear advantages, but at the same time requires technical care.

Expansion using façades, terraces and outbuildings

Not every roof is big enough for more modules. It is therefore worth looking at alternative areas. Facade modules are an option when roof space is limited. Although they are usually less efficient, they can actually have advantages in winter due to the shallow sunlight. Dirt and snow loads are also lower with vertical modules. The terrace offers another option. With a solar roof you can not only generate electricity, but also create functional sun protection.

Semi-transparent modules provide shade without significantly reducing the light. This is particularly practical for households that value aesthetics and additional benefits. Outbuildings such as garages or carports are often underestimated. Flat roofs are particularly suitable if the statics are right. Here you can create a small “charging station” that fits perfectly with an electric car. Garden houses can also be operated independently with island systems. If you think creatively, you will find numerous additional PV areas on your property.

Balcony solar systems and solar fences as additions

Even small systems can have a big impact. balcony solar systems are ideal for tenants or households with little roof space. They are easy to attach, plug into the socket and deliver up to 800 watts of nominal power. In a good location, 600 to 700 kilowatt hours can be generated per year. This is enough to operate smaller consumers such as refrigerators or routers cost-effectively. Solar fences are also becoming increasingly important. They take advantage of unused property boundaries and generate energy at the same time.

The yield depends heavily on the orientation, which is why sunny locations offer clear advantages. Both solutions are inexpensive, flexible and quickly installed. They also increase your own consumption without major construction effort. For owners of an existing PV system, balcony solar systems or solar fences can be an ideal addition. They are also a sensible introduction to solar energy for tenants or owners with small areas.

Adapting the inverter and other technology

Expanding a PV system doesn’t just mean adding modules. The technology also has to grow with it. The inverter is particularly important. It converts the direct current generated into usable alternating current. It has to cope with the new total voltage of the modules. If the voltage is below the minimum limit, it does not generate any electricity. If it is above that, there is even a risk of a defect. A calculation example makes this clear: With 10 modules, each with 35.2 volts, the maximum input voltage is 352 volts. If the system is expanded by 3 modules, it increases to 458 volts.

An inverter with an upper limit of 400 volts would be overwhelmed by this. The solution can be a larger inverter or an additional one. A second meter may also be required. When planning, specialist companies check which solution makes the most sense in each individual case. Cables and fuses must also be checked for their resilience when expanding. Anyone who saves here risks loss of yield or damage to the system.

Legal requirements and the EEG feed-in tariff

One of the most important questions in the expansion concerns the remuneration for the electricity fed into the grid. According to Section 9 Paragraph 3 EEG, several systems on one property within 12 months are considered one system. However, this only counts for determining performance. The date of the extension applies to the remuneration. This means: New modules receive the feed-in tariff valid at the time of installation. This means that the level of remuneration differs between old and new modules.

However, when replacing old modules, known as repowering, the original commissioning date remains relevant. This means: Replaced modules retain their old compensation. It is also important: Every expansion is legally considered a new installation and must be reported to the Federal Network Agency, the grid operator and the tax office. Anyone who forgets this risks legal and financial disadvantages.

Battery storage and optimization of the existing system

Expanding with new modules is not always the only way. A storage solution can be just as useful. With battery storage, you can significantly increase your own consumption. Electricity produced during the day is stored and used in the evening or at night. This reduces the dependency on the grid operator. Although the acquisition costs are high, the investment pays off in the long term. Many federal states also offer funding programs. Another approach is to optimize existing modules.

Older systems lose performance over the years. Defective modules can be exchanged or replaced with more powerful ones. Used modules are also an option if they have been tested and are functional. However, intact modules may not simply be replaced as this may violate EEG requirements. It should therefore be checked whether a replacement is considered repowering or a new system.

Conclusion

Expanding a PV system is an investment in the future. Whether through additional modules, alternative areas or storage – every measure increases independence from the grid operator. Although the expansion requires careful planning and entails additional costs, the advantages outweigh the disadvantages. More self-consumption, greater security of supply and a contribution to the energy transition are clear plus points. Anyone who observes legal requirements and incorporates specialist knowledge will make their system fit for the years to come.

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Frequently asked questions about expanding a PV system

1. Can I expand my existing PV system?

Yes, an extension is possible in many cases. It is important that there is enough roof space or alternative areas such as garages, carports or garden sheds and that the load-bearing capacity of the roof is checked. The compatibility of the new modules with the existing system must also be ensured.

2. Do I have to register the expansion of my PV system with the grid operator?

Yes, every expansion of a PV system must be registered both with the grid operator and in the market master data register. This is necessary to avoid legal consequences and the loss of compensation claims.

3. Do I need a new inverter when expanding?

It is often advisable to install an additional or more powerful inverter when expanding the number of modules. Alternatively, a multistring inverter can manage both system strings without the need for another inverter.

4. Should I also adapt my battery storage when expanding?

Yes, it is advisable to adapt the storage capacity to the expanded performance, as this can increase the self-consumption of the electricity generated. Around 1 kWh of storage capacity is usually recommended for each additional kWp of PV output.

5. Are grants or financial support available for expanding a PV system?

Yes, under certain conditions you can apply for funding such as KfW loans or regional programs for expansion. It is advisable to get advice beforehand about what funding is currently available.

6. How much does it cost to expand a PV system?

The costs for an expansion are typically between around 1,400 and 1,600 euros per kWp of additional power. Additional costs may arise for expanding the inverter or installing a larger battery storage system.