Repowering Solar Systems: Boosting Efficiency Through Modernization

Photovoltaic (PV) systems are one of the most eco-friendly methods of generating energy, but they gradually lose efficiency over time. This loss, known as degradation, means that after 25 years, a PV system may only operate at about 85% of its original capacity. This is where repowering comes in—replacing old or inefficient components with newer, more powerful parts to increase the system’s output and ensure its long-term economic viability. With the adoption of Solar Package I, the process of repowering in Germany has been greatly simplified, particularly for rooftop installations.

What is Repowering?

In the context of photovoltaics, repowering refers to the replacement of old or less efficient modules and inverters with newer, more powerful components. The goal is to compensate for and even surpass the power loss caused by aging by using modern, high-performance technology.

Imagine this scenario: A photovoltaic system installed in 2012 with a capacity of 10 kWp. The original feed-in tariff under the Renewable Energy Sources Act (EEG) was high, ensuring the system’s profitability. However, due to the natural degradation of the modules, the system’s output decreases over time, generating only 8,500 kWh annually instead of the initial 10,000 kWh.

Repowering comes into play here: By replacing the old 230-watt modules with modern 400-watt modules, the system’s efficiency can be significantly increased. According to EEG regulations, when repowering, only the original Wp capacity (in this case, 10 kWp) may be installed at the old feed-in tariffs. Since modern modules are more efficient, less space is needed for the same capacity. This opens up new possibilities.

With higher module performance, the required roof area is reduced. Suppose the original system consisted of 43 modules, each 230 watts, to reach 10 kWp. With new 400-watt modules, only 25 modules are needed to achieve the same capacity, leaving part of the roof space unused. Here, a second PV system could be installed, operating independently of the original feed-in tariff.

It would be economically counterproductive to use the repowered system’s electricity for self-consumption since the high EEG feed-in tariff remains in effect. The new system, however, could cover the company’s or household’s own power needs. This concept is a prime example of the intelligent use of resources in the energy transition.

Key Components in Repowering

Repowering mainly involves two crucial components:

1. Modules: Older solar modules have lower efficiency compared to current models. Modern modules now offer efficiency rates of 19-22%, compared to 14-16% for modules installed 10 years ago. Replacing them directly increases electricity generation.

2. Inverters: Inverters, which convert the direct current from the modules into alternating current, also age. Their efficiency can decrease over the years. New inverters operate at an efficiency of 98% or higher, significantly boosting the system’s overall performance. Moreover, modern inverters can handle higher voltages, which is necessary when retrofitting with more powerful modules.

Solar Package I: Simplifications for Rooftop Repowering

With Solar Package I, approved on August 16, 2023, and enacted on May 16, 2024, significant relief has been introduced for repowering rooftop installations. The bureaucratic effort to replace inefficient modules has been reduced, allowing for replacement even when the modules are still functional. Additionally, new modules can inherit the feed-in tariff of the existing system, even if they are more efficient. This can be financially advantageous, especially for older systems with higher tariff rates. Solar Package I makes it even more economically attractive for rooftop system operators to modernize and benefit from technological advances.

Benefits of Repowering Solar Systems

• Increased Performance: Replacing old modules with modern, more efficient models can nearly double the installed capacity on the same surface area.
• Higher Yields: Newer modules and inverters lead to a significant increase in annual electricity production.
• Extended Lifespan: New components come with a warranty of 20 to 25 years, ensuring the system’s operation for decades to come.
• Economic Viability: Systems benefiting from higher feed-in tariffs can generate additional electricity production, making repowering financially lucrative.
• Climate Protection: The increased electricity production from renewable sources directly contributes to reducing CO₂ emissions.

Germany has around 2 million PV systems, many of which were installed over a decade ago. It is estimated that approximately 10-15% of these systems could be eligible for repowering in the next five years, equivalent to around 200,000 to 300,000 installations that could be upgraded to the latest technology.

Market Potential for Repowering

Installations made between 2005 and 2015 are particularly affected, as they are already experiencing significant yield losses due to degradation, and the technology used is outdated. Many of these systems also benefit from feed-in tariffs significantly higher than today’s rates, making repowering even more appealing.

The market for repowering solar systems is growing. According to a study by the German Energy Agency (dena), the repowering market could grow by 50% over the next five years as more system operators recognize the potential to modernize their old installations. The combination of falling solar module prices and the benefits of repowering makes this market especially attractive.

By 2030, it is expected that around 500,000 PV systems in Germany will be repowered, leading to a significant increase in installed capacity and electricity production.

C2sun Experts' Conclusion

Repowering solar systems is a key strategy to restore the performance of older installations and pave the way for a sustainable, economically attractive future. Technological advances in recent years allow modern solar modules and inverters to provide significant performance gains—even when using the same area.

With the new regulations in Solar Package I, repowering rooftop installations in Germany has been further simplified, benefiting both system operators and the entire energy market. As many older systems will need modernization in the coming years, the repowering market presents significant opportunities for installers and system operators.

For solar system operators aiming to boost efficiency, now is the perfect time to consider repowering. The combination of higher yields, extended lifespans, and financial benefits makes repowering a worthwhile investment in the future.

By 2030, the repowering market in Germany alone could reach a volume of several billion euros, making it a central component of the energy transition.