The Stromspeicher Inspektion 2019 survey: RCT Power’s battery storage system is best in class for under-8 kWh capacity


The HTW Berlin’s latest power storage survey examines the efficiency of PV storage systems available in Germany. According to HTW Berlin, a high battery efficiency alone is no guarantee for a highly efficient system. Decisive factors for overall high energy efficiency are low conversion and standby losses for the entire storage system.

The HTW Berlin selected 16 systems for the 2019 survey. The RCT Power System, consisting of the Power Storage DC 6.0 and the Power Battery 5.7 was ranked first in the category for systems with a storage capacity of less than 8 kWh. The overall result, in competition with larger storage systems, showed the RCT Power System in the top three.

Thomas Hauser, managing director of RCT Power GmbH, explains why the study is so interesting.

RCT Power achieved a top rating in the 2018 survey, which was then conducted for the first time. This result was confirmed and repeated in this year’s, 2019 edition of the survey. Mr Hauser, did you expect this result?

We know that we offer a very efficient and dynamic battery storage system. However, we were curious about how we would perform in 2019 as we don’t have a glimpse behind the scenes of other manufacturers.

The RCT Power System again took second place overall in all categories. Are you satisfied?

This result is excellent news for our customers. The HTW Berlin certifies that we have the best system in the range up to 8 kWh energy storage capacity. System sizes in the range between five and 8 kWh are ideal for residential buildings and are therefore in high demand. In summary, we are absolutely delighted with this great result.

Why is the system so excellent?

A system can only be excellent if it is backed up by a strong team with a lot of experience and a strong drive for continuous innovation. We believe in the sustainability of solar energy. We have taken a serious look at the problems of existing battery storage systems. We have also completely rethought storage technology with the ambitious goal of developing the most efficient, sustainable and flexible storage system. This approach is making a real contribution to protect our climate.

The RCT Power System eclipses competitors with a settling time of four tenths of a second. What is the benefit for system owners?

The settling time allows a system to react quickly to demand.  The system, for example, is able to follow the start-up currents of refrigerators and freezers and then cover these as simultaneously as possible from the storage system. With slower systems, the consumer energy demand from the storage system is always lagging. As a result, electricity is first used from the public grid and only later from the storage system. Every watt that you generate yourself and do not draw from the public grid is valuable. This becomes very obvious at the end of the year when the electricity drawn from the grid is being added up and the bill is presented. Our system manages to access and use the self-generated solar power in fractions of a second and thus reduces the energy drawn from the grid significantly.

One of the key takeaway findings of the 2019 survey is that the total system efficiency is determined, among other factors, by the conversion and standby losses of the entire storage system. Can you explain in more detail?

Conversion and standby losses are reflected in the amortization time. Every system owner faces this decisive question: “How long do I have to operate a system until I have generated the number of kilowatt-hours and its monetary equivalent to cover the initial set-up costs of the system?” In the context of protecting the climate, the question can be reworded: “How long do I have to operate a system before I have generated the amount of energy that was required to manufacture the system in the first place?” RCT Power’s high efficiency means it performs significantly better than other products. This leads to a reduced financial amortization period and surplus renewable energy is available earlier in the system’s life cycle. That’s efficiency that really supports sustainability.

The 2019 survey had a total of 16 companies participating. Only eight of these 16, including RCT Power, have submitted system readings from tests that were performed by independent laboratories. Is the study meaningful?

Yes, the survey is indeed very meaningful. The competition is open to all and every manufacturer can enter their system. However, only the best have probably decided to participate with independent laboratory results. The yardstick for system performance has been set and not just since the 2019 survey. We will continue to push the limits of system performance. The results of the survey allow us to showcase to our customers that they have bought a great system.