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09.02.2024 - Energy storage inspection 2024: RCT Power, BYD, Fronius and KOSTAL on the winners' podium

Energy storage systems are now a standard in many European countries when installing a residential photovoltaic system: For instance, according to the German Core Energy Market Data Register (Marktstammdatenregister), almost four-fifths of new solar installations with an output of 2 to 20 kWp had a battery storage system on board in 2023.

In total, over 570,000 new home storage systems were installed in Germany last year, thus, doubling the number in just one year.

The Berlin University of Applied Sciences (HTW) has made it its mission to analyse the efficiency of the storage systems that are available on the market. Since 2018, it has been determining the respective system efficiency (System Performance Index, SPI) to improve comparability of the storage systems on offer and analysing possible dimensioning, conversion, control and standby losses.

In the newly published – now seventh edition of the Energy Storage Inspection (Stromspeicher-Inspektion) it examined a total of 20 energy storage systems from 14 manufacturers.

Four manufacturers from our brand range landed on the winners' podium in 2024: Congratulations to RCT Power, BYD, Fronius and KOSTAL!

Another double victory for RCT Power: For the second time in a row, the company from Southern Germany has provided the storage system with the highest overall efficiency in the 5 kW and 10 kW category. In the 5 kW category, the DC storage system comprised of RCT Power Storage 6.0 and Power Battery 7.6 achieved the efficiency class A and an SPI of 92.6 %. In the 10 kW category, the combination of the hybrid inverter Power Storage DC 10.0 and the Power Battery 11.5 leads the rankings by a wide margin.


Strong performance by Fronius: The Primo GEN24 6.0 Plus in combination with the BYD Battery-Box HVS achieved the highest efficiency in the 5 kW category and the same SPI as the test winner from RCT, only differing from the second decimal place onwards. The low conversion losses of the tested system are particularly noteworthy. In the 10 kW category, the system consisting of Symo GEN24 Plus and Battery-Box HVS 10.2 took a respectable third place. With an SPI of 95.4%, it landed in the highest efficiency class.

KOSTAL ranked high in both categories: The PLENTICORE plus (G2 model) in combination with an HVS battery from BYD secured a spot in the top 5 and was ranked third in the small system segment up to 5 kW. In the 10 kW category, the combination of KOSTAL PLENTICORE plus G2 10 and the BYD HVS 12.8 had an SPI of 94.9%, which corresponds to the highest efficiency class.


BYD was also particularly proud of its performance: The Battery-Box HVS made it into the top 3 several times in both categories, always in combination with different inverters. The BYD high-voltage battery was therefore the most strongly represented product in the list of winners. This once again demonstrates the quality and versatility of the Battery-Box Premium in a wide range of application scenarios.

Another interesting topic for solar enthusiasts and professionals alike which is covered in this year’s Energy Storage Inspection, is the subject of "self-sufficiency". By providing operating data of solar electric systems, our partner KOSTAL has supported HTW’s analyses on this topic. According to the report, single-family households with a solar electric system and a storage system achieve an average degree of self-sufficiency of 70 %. There is a direct correlation between self-sufficiency and electricity consumption: the higher the consumption, the lower the degree of self-sufficiency.

The report, manufacturer responses and information on other technically relevant parameters for storage systems (e.g. partial load efficiency of the inverter) can be found via the links below. For availability and your purchasing conditions for the products, please check our QuickShop.

Link: Energy Storage Inspection Report (2024) (German)

Link: Website Energy Storage Inspection (German)

Link: BYD press release (English Version)

Link: KOSTAL News (German)