Stem's PowerTrack EMS Enables Hybridization of Two Operating Utility-Scale Solar Plants in Hungary

Stem, Inc. (NYSE: STEM), a global leader in AI-enabled clean energy software and services, announced that Solarmarkt Group, together with engineering, procurement, and construction (EPC) partner Pannonwatt Energetikai Megoldások Zrt. (Pannonwatt), has selected Stem's PowerTrack™ Energy Management System (EMS) as the integrated energy management, power plant control (PPC), and SCADA platform for the hybridization of two operating utility-scale solar plants in Hungary, establishing one of the most advanced digital renewable energy hubs in Central and Eastern Europe.

The projects will add a 40 MW / 80 MWh battery energy storage system to each of Solarmarkt Group's existing 60 MWp solar facilities: one in Szihalom and one in Hódmezővásárhely. Once completed, each site will operate as a fully integrated hybrid renewable asset. Commercial operation of the fully hybridized assets is expected by September 2026.

Stem previously supplied the power plant control (PPC) capabilities for the solar facilities in 2025 and 2026 using a hybrid-ready PowerTrack architecture. Under the new five-year agreement, the same software and controls foundation will expand across the battery systems at each site, enabling solar generation, storage, grid interconnection, and market dispatch to operate through a single integrated solution.

The hybridization of the Szihalom and Hódmezővásárhely plants also strengthens the physical renewable-energy foundation of Solarmarkt Group’s Green Cloud Platform. The platform connects renewable generation with corporate energy consumers, supporting their decarbonization objectives through traceable, auditable physical green-energy solutions. By combining solar generation with battery storage and advanced controls, the projects can help make renewable electricity more controllable, more flexible and fully prepared for cross-border, value-stacking opportunities as Central and Eastern European energy markets become increasingly interconnected.

"This project demonstrates how operating solar plants can evolve into hybrid assets without replacing the existing controls foundation," said Matt Tappin, President of Software at Stem. "Because PowerTrack EMS was designed with hybridization in mind, we can extend the platform across the battery systems while preserving the controls and operating experience already in place. This gives owners a more efficient path to adding storage and a clearer view of both technical and commercial performance."

At each facility, PowerTrack EMS will coordinate solar generation, battery dispatch, grid constraints, and market dispatch instructions while maintaining compliance with E.ON distribution-system requirements. The initial commercial strategy will focus on participation in Hungary's automatic Frequency Restoration Reserve (aFRR) market, with the platform designed to support future Frequency Containment Reserve (FCR) services and cross-border, value-stacking opportunities as Central and Eastern European energy markets become increasingly interconnected.

“For us, this project is about creating a platform that allows us to continuously understand and improve the technical and commercial performance of our assets," said Miklos Mormer, Chief Technology Officer, Solarmarkt Group. "PowerTrack EMS provides transparency into the performance and economics of both the solar and battery systems at each site, while allowing them to operate as coordinated hybrid assets. It also gives us a foundation that can evolve as Hungary's ancillary-services market develops."

Executing a project of this scale and complexity in a rapidly evolving market requires deep localized engineering excellence," said Róbert Vőneki, Chief Executive Officer at Pannonwatt. "Pannonwatt’s advanced grid-integration capability, combined with Stem's utility-scale software, will help mitigate execution risks. We are building infrastructure that is setting the technical benchmark for how existing solar assets across Europe can adapt to the future grid.

The projects reflect a broader shift across European renewable-energy markets as owners add battery storage to operating solar facilities to increase flexibility, reduce curtailment, and create new sources of value. The collaboration among Solarmarkt Group, Pannonwatt, and Stem provides a model for converting existing solar plants into integrated hybrid renewable assets while retaining established plant infrastructure and controls.

Stem | stem.com