As part of the SUN BOX project, one of our first technical activities was to identify battery storage solutions suitable for plug-in balcony photovoltaic (PV) systems and applicable in our pilot countries: Bulgaria, Lithuania and North Macedonia.

To support this process, the project team conducted a comprehensive market assessment covering more than 50 battery storage products currently available on the European market. The evaluation considered technical, economic and practical criteria, including storage capacity, purchase price, expandability, safety features, weather resistance, market availability, compatibility with balcony PV systems and ease of installation.

A particular focus was placed on solutions that can realistically be deployed in multi-apartment buildings. The availability of products in the participating countries, shipping options, warranty conditions and the overall user experience were therefore considered alongside technical specifications.

From More Than 50 Products to Six Finalists

The market analysis identified a large number of technically suitable systems. However, many products were excluded because of limited market availability, uncertain delivery conditions, missing product information, higher costs, lower maturity, or limited suitability for the project objectives.

Based on the assessment, six battery storage solutions were selected for further consideration within the SUN BOX project:

• Anker Solarbank 2 E1600 AC
• EcoFlow Stream AC Pro
• EcoFlow Stream Max
• EcoFlow Stream Ultra
• Zendure SolarFlow 1600 AC+
• Zendure SolarFlow 800 + AB2000X

These systems represent some of the most mature and widely available balcony PV storage solutions currently offered on the European market.

Key Findings

The selected systems provide storage capacities between 1.6 kWh and 1.92 kWh, making them suitable for typical balcony PV installations. Prices ranged from approximately €599 to €779 at the time of evaluation, resulting in storage costs between approximately €340 and €406 per kWh.

All selected systems are designed for outdoor installation and offer high protection against dust and water ingress (IP64 to IP67). Most systems can be expanded to storage capacities exceeding 11 kWh, providing flexibility for future household energy needs. An additional advantage is the integration of smart energy management features and compatibility with modern smart-meter solutions, enabling more efficient use of locally generated solar electricity.

Supporting the Upcoming Pilot Installations

The selected battery storage systems will form the basis for the next phase of the SUN BOX project. Over the coming months, the project partners will continue to assess market availability, logistics, installation requirements and user acceptance in the participating countries. The results will support the selection of suitable systems for demonstration activities and help identify practical pathways for increasing self-consumption of solar energy in multi-family residential buildings.

Disclaimer: The systems presented in this overview were selected solely for evaluation within the SUN BOX project. Their inclusion does not constitute a commercial recommendation, endorsement or advertisement. The assessment was conducted according to project-specific technical and practical criteria.

Authors: M. Sc. Christoph Johann and Martin Liske, DGS - Deutsche Gesellschaft für Sonnenenergie, www.dgs-berlin.de