Germany’s power system recorded its sharpest known demand jump from commercial refrigeration on Monday, after 6,380 supermarket chillers across 11 states began heating their coils within a 74-second window. The 412-megawatt spike was roughly the output of a large power station, according to measurements reviewed by the Rhine Current Control, a regional grid-balancing operator.
The surge began at 04:17, when a routine software update from refrigeration provider FrostWerk Systems sent a maintenance signal that the units interpreted as a command to defrost. Grid frequency briefly fell to 49.82 hertz, below Germany’s standard 50 hertz, before reserve power restored it. No customers lost electricity, but operators say a longer pulse could have forced emergency limits.
A signal became a command
Max Kennedy, an operations analyst at Rhine Current Control, said dispatchers first suspected a faulty meter because the load climbed so quickly. “We had never seen thousands of independent cooling systems behave like one machine,” he said. A review of control-room readings and device logs later showed the units receiving the same timestamped instruction, rather than responding to local temperature changes.
FrostWerk said a cloud-service update had confused a maintenance heartbeat with approval to begin a defrost cycle. The company said its engineers had disabled the affected service and that there was no evidence of outside access. The update was intended for a small staged test; instead, it reached devices connected to 214 grocery distribution sites and stores.
Shania Hauck-Bins, the company’s chief technical officer, said the firm had not understood that several models would treat the signal as an immediate command. “Our safeguards were designed to prevent a bad setting, not a perfectly valid message arriving everywhere at once,” she said. FrostWerk has suspended remote updates while it checks how each model handles maintenance signals.
Stores face a cold-chain check
Store operators spent Monday checking temperature records and moving stock where needed. FrostWerk said chilled cabinets peaked at 8.7°C (47.7°F) at 17 sites, while freezer alarms showed no readings above -11°C (12.2°F). Those locations have set aside affected products for review; Germany’s food-safety rules require operators to assess each item’s storage history before sale.
Emre Yetkiner, who manages a grocery warehouse outside Leipzig, said staff found the alarm just after opening the control room. “The screens showed a normal night, then every defrost timer lit up together,” he said. The warehouse’s backup cooling kept its main rooms within their operating range, but staff checked 46,000 cartons before releasing shipments.
The affected retailers estimate that delayed deliveries and product checks could cost them €38 million (about $44 million) if the checks extend through the week. Germany’s federal energy regulator has asked FrostWerk and grid operators for a timeline of the event and a list of connected devices. It has also urged operators of large cooling systems to disable unattended group commands until new safeguards are tested.
