The University of Applied Sciences (HTW) Berlin has published its annual Energy Storage Inspection. In addition to the efficiency of home storage systems in the 5 kW and 10 kW performance classes, the eighth edition of the efficiency study also tested the forecast-based energy management systems of some manufacturers for the first time.
With over 580,000 solar power storage systems installed in 2024, the German home storage market is stabilizing at a high level, once again highlighting the importance of high-quality storage systems. Using the System Performance Index (SPI), the HTW Berlin compares storage systems in terms of storage capacity, performance, conversion efficiency and standby power consumption, among other things. A total of 22 battery systems from 17 manufacturers were tested, with ten of the systems achieving the highest efficiency class A. In the process, the new hybrid inverter from KOSTAL set a new efficiency record of 98.2 %.
Four of our brand manufacturers made it onto the winners' podium again this year: RCT Power, KOSTAL, BYD and Fronius.
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Once again, the high-quality power storage systems from RCT Power are the most efficient battery storage systems on the market. The combination of the hybrid inverter Power Storage and Power Battery achieve top values in both categories, with an SPI of 92.6% in the 5 kW category and 96.4% in the 10 kW category.
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The Fronius hybrid inverter Primo GEN24 6.0 Plus took second place in the 5 kW category in combination with the BYD Battery-Box HVS 7.7. The Symo GEN24 10.0 Plus was still able to take third place in the 10 kW category in combination with the BYD Battery-Box HVS 10.2 – both devices were able to achieve energy efficiency class A with their SPI.
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This year, KOSTAL is once again impressing with the latest PLENTICORE generation and demonstrating outstanding results that underscore the progress made in increasing efficiency and optimizing systems. With the new Plenticore G3 hybrid inverter, Kostal has set a new efficiency record of 98.2 % in charging mode. In combination with the BYD Battery-Box HVS, the Plenticore G2 was also able to achieve energy efficiency class A. |
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BYD was once again able to demonstrate the quality and versatility of its Battery-Box HVS in combination with various inverters. In both the 5 kW and 10 kW categories, the Battery-Box was one of only two battery systems to achieve an A rating in both categories. |
In addition to the comparison of electricity storage systems, HTW Berlin and the Karlsruhe Institute of Technology have developed a new test procedure that can compare the quality of forecast-based energy management strategies. The criteria include, among other things, grid support and functionality, the influence of energy management on the aging of battery systems and the quality of PV peak shaving. The six energy management systems tested also include those from the manufacturers FENECON, KOSTAL and RCT Power.
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In particular, the AI-based forecasting method of the FENECON FEMS energy management system performed extremely well. It can be individually configured to a specific risk level, works without an internet connection and external weather data, and charges the battery with the most efficient performance at the latest possible time, thus treating the battery particularly gently.
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The report, manufacturer responses and information on other technically relevant parameters for storage systems can be found via the links below. For availability and your purchasing conditions for the products, please check our QuickShop.
Link: Storage Energy Inspection 2025 from the HTW Berlin (in German)
Link: Website Storage Energy Inspection (in German)
Link: HTW Berlin 2025 energy storage inspection: Kostal, SAX Power set new efficience records (PV Magazine energy storage)
Link: KOSTAL news
Link: BYD press release
