Proof‑of‑Warmth: Wedding Startup Hides Crypto Miners in Radiators, Landlords Charge Rent for Your Boiler's Side Hustle

RadiantChain, a small proptech firm operating out of a co‑working loft in Wedding, quietly began retrofitting old cast‑iron radiators with compact cryptocurrency hashboards this winter — then offered landlords a new line item to invoice tenants: “heat yield.”

The scheme started as a pilot two months ago, company founder Elias Baum told a tenant meeting: "We provide passive heat income — your boiler pays for itself and residents profit from CozyCoin." Residents first noticed the change when radiators hummed at odd hours and electricity bills spiked even while rooms sat empty. "I woke up and my radiator was purring like a small server farm," said tenant Ayşe Yılmaz, who runs a corner bakery once famous for its morning simit. "They were making money off my bread shop's warmth and then asking me to pay more."

RadiantChain installs stacked hashboards inside radiator casings, vents the boards into the building's supply circuit, and funnels excess heat to wellness apps and cloud customers who pay for “ambient coziness.” Landlords began advertising flats with a new “heat‑yield” tag — expected monthly returns listed next to exposed brick — and some pushed rents upward under the euphemism of a “building revenue share.” Property manager Janek Fischer of Licht & Co. defended the invoices: "We are capturing value that was previously wasted."

The reaction was immediate. Tenants reported receiving surprise bills described as “boiler partnership fees”; a tenants' group formed an emergency WhatsApp chain and a lawyer offered sliding‑scale legal advice. Bezirksamt Mitte issued a terse statement: "We are aware of installations that may violate building and energy codes. Inspections are scheduled." Police confirmed they have opened a preliminary inquiry into suspected fraud and unlawful modification of heating systems.

Critics say the scheme is the latest example of extractive entrepreneurship: turn a basic necessity into a commodity, rebrand tenants as micro‑investors, then bill them for their own heat. "It's a thermal panopticon," said urbanist Dr. Lena Köhler, citing Foucault and laughing coldly. "If Kafka had to pay his radiator's side hustle, Josef K. would have been condemned before his trial."

RadiantChain insists users opt in and can keep CozyCoin; tenants say consent forms arrived after the miners were installed. Meanwhile district inspectors will begin audits next week, and a local Mietverein plans a collective complaint. In the short term, flats listed as “heat‑yield” remain on the market and bills keep arriving — leaving residents to decide whether to unplug their radiators, fight in court, or buy into the micro‑economy that now warms their homes.