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The SOLMATE demonstrators are progressing on all fronts, moving from early technical specifications toward a complete system design that is ready for installation and testing.

In recent months, SunCrafter [SUNCRAFT], overseeing the plug-in PV (PiPV) demonstrator, conducted a desirability assessment showing rising public interest in small residential solar units coupled with battery storage. PiPV systems are compact (<2 kWp) photovoltaic systems that can be plugged into a standard household power socket and feed self-generated (solar) electricity directly into the house power–grid to reduce grid-power consumption.

Germany’s progressive policy framework supporting decentralised energy systems, combined with technological advancements and declining equipment costs, has made small-scale PV systems increasingly attractive to end-users. Up to 5 million German households have already installed their own PIPV system as market data suggests.

In a survey conducted as part of the SOLMATE project, 88% of respondents indicated that integrating a battery into their new or existing system is important to them. Batteries increase self-consumption by storing excess solar generation for use during evening hours or periods of low production, thereby reducing grid imports and improving overall energy cost savings. This is particularly relevant for PIPV setups as they generally do not receive feed-in-tariffs for surplus production.  

Most respondents expressed a preference for EU-manufactured equipment and stated that they would be willing to pay a premium for it. At the same time, some uncertainty remains regarding the longevity of second-life batteries. However, presenting the option of warranty conditions comparable to those of new battery systems significantly reduced this concern among participants. 

Simple and ready to be installed in German households

The final PiPV setup proposed by SunCrafter features second-life PV modules tested by CEA and CERTISOLIS, a 5 kWh second-life lithium iron phosphate (LFP) battery supplied by Watt4Ever, and a hybrid micro-inverter.

Thanks to the rapidly evolving technological developments in the sector, the design has evolved considerably since the first specifications. Its layout has been greatly simplified by reducing the number of external components and interfaces. This update minimises installation and operational errors, while increasing overall user friendliness. This simplification has been possible with the commercialisation of new hybrid inverter units that integrate multiple functionalities into a single device. These units can operate in both grid-connected and limited off-grid modes, providing reliable backup power in the event of a grid outage. 

Thanks to smart system integration, solar generation, household electricity consumption, and battery status can be monitored in real time. This facilitates installation, troubleshooting, and performance optimisation. Compared to earlier concepts, all components are EU-compliant, housed in weather-resistant enclosures, and equipped with a single standard communication and monitoring interface (Wi-Fi and Bluetooth). The PiPV demonstrator is therefore technically ready for residential deployment. 

Pilot phase and performance evaluation

In Q2 2026, three demonstration systems will be installed in households across Germany. Electricity generation, household electricity consumption and grid imports will be monitored over a 12-month period. The results will be used to compare each household’s total energy use, including imported and self-generated electricity, before and after installation, in order to assess the economic benefits of the 2nd life PiPV systems. Based on data collected from PV generation and battery performance, a simulation model will also compare system configurations with and without battery storage. This will help validate the added value and necessity of integrating a battery under different usage patterns.

Business model and economic outlook

The business model reflects the updated system design. With second-life PV modules now integrated into the setup, CEA becomes a central supplier within the value chain. The value proposition has evolved from a battery add-on to a complete small-scale energy system. While the compact layout allows less room for customisation, it simplifies installation and operation. 

With technical feasibility and testing completed, the main open question concerns economic competitiveness. The current cost of the demonstrator systems exceeds both the average market price of new battery systems and the target price identified in the survey. 

Whether PiPV systems using second-life batteries and PV modules can compete with new systems on the market will depend on several key factors: 

• reduced processing and logistics costs 
• easier access to used EV batteries in Europe 
• competitive warranty conditions for second-life components 
• supportive policy frameworks and technical standards 
• final pricing of second-life PV modules and batteries 

A full review will only be possible once the pilot systems are installed and running. 

© visual Adobe Stock | U. J. Alexander