KOSTAL honoured as test winner of the HTW electricity storage inspection 2026

In the 2026 electricity storage inspection by HTW Berlin, KOSTAL achieved test victory in the 10 kW class (AC-coupled) with the PLENTICORE G3 M 10 in combination with the BYD Battery-Box Premium HVS 12.8. The independent study thus confirms the high system efficiency and performance of the KOSTAL storage system in the demanding application environment of modern residential buildings.

The study is based on detailed laboratory measurements and a simulation-based annual assessment using the System Performance Index (SPI). Not only the pure efficiency of individual components is assessed, but also the efficiency of the entire PV storage system under realistic operating conditions.
 

KOSTAL receives multiple awards for system performance

• Test winner in the 10 kW class
  KOSTAL PLENTICORE G3 M 10 (AC) + BYD Battery-Box Premium HVS 12.8
• Very high efficiency
  KOSTAL systems achieve efficiency class A (95.1 % / 10 kW)
• Best individual efficiency
  Best PV2BAT efficiency for KOSTAL Hybrid inverters
• Very good value in standby consumption
  PLENTICORE G3 MP systems with only 6 W at Min-SoC
   

Very high efficiency in the overall system

The KOSTAL system achieves an SPI value in efficiency class A in the 10 kW class, making it one of the most efficient storage systems on the market. Particularly noteworthy is the very high efficiency of the energy conversion from PV generation to battery charging (PV2BAT), which contributes significantly to the high overall performance.

Energy efficiency as a key quality feature

"The award as test winner emphasises our claim to develop inverter and storage systems that are powerful and - holistically - efficient," says Andreas Schmalenberg, Product Manager at KOSTAL. "Especially in combination with heat pumps, electromobility and dynamic electricity tariffs, system efficiency is crucial for cost-effectiveness and future security."

The electricity storage inspection by HTW Berlin is one of the most renowned independent comparative studies for PV storage systems in the German-speaking world. In the 2026 edition, only systems that already have a high level of efficiency were analysed - making the top ranking achieved all the more significant.

AC or DC. Single-phase or Three-phase. KOSTAL delivers.

KOSTAL was the only manufacturer in this year's comparison to include four systems in the electricity storage inspection. This means that KOSTAL is represented in both the 5 kW and 10 kW classes - with both AC and DC-coupled systems.

What's more, KOSTAL demonstrates high system efficiency not only in a single configuration, but also across different power classes, coupling types and single-phase and three-phase system architectures. The results confirm the high efficiency of the KOSTAL system platform across different grid phases and system architectures.

Why is the SPI seal relevant?

The SPI seal (System Performance Index) of the HTW Berlin serves as a reliable benchmark for the selection of photovoltaic storage systems. The HTW independently evaluates the overall performance of a system in real operation - precisely what is crucial for making well-founded purchasing, planning and product range decisions.

The SPI seal creates more transparency and security for system operators: the SPI clearly shows how efficiently a system works in everyday operation and what contribution it makes to higher self-consumption and lower electricity costs. Or to use a simple rule of thumb: A higher SPI means more self-consumption, less electricity drawn from the grid and lower electricity costs.

The SPI provides installers with an independent decision-making and argumentation aid. The holistic assessment reduces planning risks, facilitates system design and supports comprehensible, technically sound customer advice.

With clear efficiency classes and a practical methodology, the SPI seal provides guidance - from the initial consultation to the long-term investment decision. Since 2018 and for the ninth time in a row, KOSTAL has been one of the best systems in the independent comparison.