Investing in VREY

If Europe is serious about reaching its climate targets, the way we produce and consume energy in cities must fundamentally change. While new buildings are increasingly built to be energy-efficient, the real transformation challenge lies in the existing stock of the millions of apartment buildings across the continent, that were never designed with decentralized energy in mind.

Germany in particular has entered a new regulatory phase. From 2025 onward, extensive measures will require building owners to comply with more ambitious energy standards. These include rooftop solar obligations for renovated residential buildings, stricter efficiency rules for heating systems, and new carbon pricing schemes under the EU Taxonomy. For landlords, this means: waiting is no longer an option.

The problem is, even for those who want to act, the system has made it nearly impossible, especially in the case of multi-tenant buildings. Selling self-generated solar power directly to tenants has historically required landlords to register as full energy suppliers, navigate complicated metering infrastructure, and comply with a web of regulations that were never designed for decentralized energy models. The result? Minimal adoption, slow change, and a regulatory paradox: the buildings most in need of solar are the ones least able to implement it.

This is where VREY comes in. The Berlin-based startup has built a fully integrated software platform that removes the core barriers to bringing rooftop solar to multi-tenant buildings. Their approach is built around a little-known but powerful new law: §42b EnWG, part of what is colloquially known as "Solarpaket 1", a key legislative package passed by the German government to accelerate the energy transition in the housing sector.

In essence, Solarpaket 1 and §42b in particular introduce a new legal model for what’s called gemeinschaftliche Gebäudeversorgung, or “shared building energy supply.” For the first time, it allows landlords to sell solar power generated on their rooftops directly to tenants without having to become official utility companies. The regulation simplifies the compliance process, streamlines billing, and eliminates the need for costly and complex market roles that previously made tenant electricity (or Mieterstrom) models unattractive.

What VREY has done is translate this legal innovation into a working product. Their platform combines BDEW-certified metering infrastructure, automated billing software, and tenant onboarding tools into a single solution. What previously took six months of coordination with utilities, consultants, and installers can now be done in a matter of weeks. VREY gives landlords a plug-and-play way to meet regulatory requirements, generate new income from their rooftops, and provide tenants with clean, locally produced electricity at a lower price than traditional utility tariffs.

But the vision doesn’t stop there. VREY sees itself not just as a billing tool, but as an energy operating system for buildings. In the coming months, the platform will be extended to cover heat pump compliance and heating cost allocation, enabling full coverage of renewable heating obligations.

So why did we invest?

At STYX, we look for founders who build not just for today’s pain points, but for the structural shifts shaping tomorrow. The two founders Julius Pahmeier and Cedric Jaeger bring the right blend of deep technical expertise and a proven track record of execution, grounded in experience across energy systems, real estate, and strategy consulting including their time at Roland Berger.

The market they’re tackling is massive. Over 1.9 million multi-tenant buildings in Germany fall under the scope of new solar and heating mandates. VREY’s model also reflects something we deeply believe in: making climate tech not just environmentally necessary, but economically rational. By aligning landlord incentives with tenant benefits and regulatory realities, VREY creates a win-win-win scenario and shows how the urban energy transition can move beyond pilot projects into scalable, permanent infrastructure. We’re proud to be part of this journey and excited to support the team as they bring solar to the rooftops and tenants of Germany’s cities.