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2023 Energy Storage Inspection – Fronius GEN24 plus impresses in all reference cases with improved System Performance Index

Energy storage

New year, new top rankings: Fronius was once again able to impress at the 2023 Energy Storage Inspection by HTW Berlin – University of Applied Sciences. In both reference cases tested, we were able to improve the System Performance Index with Fronius GEN24 Plus hybrid inverters and the BYD Battery-Box Premium. Fronius is also once again one of only two manufacturers to achieve efficiency class A in both reference cases.


Independent testing institutes test the overall efficiency of storage systems, analyzing the interaction of the PV system and battery storage. Two different reference cases are used for the evaluation.

The first reference case analyzes the System Performance Index (SPI) for a 5-kW PV system with annual household consumption of 5,010 kWh/a, while the second reference case combines a 10-kW PV system with heat pump (2,664 kWh/a) and electric car (1,690 kWh/a), and annual household consumption of 5,010 kWh/a.


  • In the 5 kW reference case, Fronius Primo GEN24 6.0 Plus together with BYD Battery-Box Premium HVS 7.7 achieves an SPI of 92.6%.
  • In the 10 kW reference case, Fronius Symo GEN24 10.0 Plus inverter with BYD Battery-Box Premium HVS 10.2 achieves an SPI of 95.4%.

» Using the System Performance Index, anyone can immediately see which system is most efficient and how much energy each system actually provides. «

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Pfaffenbichler Dominik, Development at Fronius International

Why is the System Performance Index (SPI) determined during the Energy Storage Inspection so valuable? Why should installers and consumers also pay attention to the SPI? And what makes Fronius inverters so successful in the Energy Storage Inspection? 

Dominik Pfaffenbichler, who works in Development at Fronius International offers exciting answers:

What makes the System Performance Index (SPI) so special for you compared to other key indicators?

DP: What’s really great about the SPI is that it doesn’t just take the conversion efficiency of an inverter into account, but instead includes all the relevant losses of a storage system, which makes it possible to achieve a holistic analysis and to fairly compare different systems.

Who can participate in the Energy Storage Inspection?

DP: Any inverter manufacturer. The only important thing is that measurements are done at an independent testing institute using series production (hardware and software), and that the deadlines are met.

This year, some parameters for the SPI were adjusted, which changed the results of all system combinations. How did this come about and what was adapted?

DP: Changes were made to general conditions, such as elimination of the 70% feed-in limit, as well as the difference between feed-in tariff and grid purchase price. The SPI has always been dynamic and takes into account user scenarios as well as feedback from us participants to improve the methodology

How is it possible that Fronius has achieved top rankings for the past 4 years?

DP: A lot of hard work has gone into that. We analyze the SPI as well as the results from each Energy Storage Inspection and incorporate all findings into the (further) development of our hardware and software. We never stop optimizing our system.

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