Clean heat from deep underground: a closed-loop geothermal plant delivers power in Germany

Geothermal energy has always carried a frustrating asterisk. The heat beneath our feet is enormous and endlessly renewable, but conventional geothermal plants can only tap it where nature has conveniently supplied hot underground water and porous, permeable rock — a short list of lucky geologies. In Geretsried, Bavaria, the Canadian company Eavor has demonstrated a way to loosen that constraint, and POWER Magazine reported the milestone.

On December 4, 2025, Eavor's first commercial-scale "Eavor-Loop" delivered its first electricity to the grid. Instead of relying on natural reservoirs, the system drills two vertical wells connected by a lattice of horizontal branches — six laterals each, roughly 16 kilometers of continuous wellbore per pair — and seals them into a closed circuit. A working fluid flows through this underground radiator, absorbing heat from the surrounding rock by conduction alone. There are no pumps: the difference in fluid density between the hot and cold sides drives circulation on its own, a design the company calls a thermosiphon.

“The heat beneath our feet is enormous and endlessly renewable, but conventional geothermal plants can only tap it where nature has conveniently supplied hot underground water and porous, permeable rock — a short list of lucky geologies.”

Because it does not depend on finding underground water, rock permeability or a continuous water supply, the approach sidesteps several of geothermal's historic headaches at once — including the exploration risk of drilling and finding nothing, the need to source and treat water, and the small earthquakes sometimes triggered by injecting fluid into rock. When fully built out with four loops, the Geretsried site is designed to deliver 64 megawatts of heat and 8 megawatts of electricity.

The people behind it are frank about its promise. Eavor President and CEO Mark Fitzgerald said the company is "more confident than ever that our closed-loop geothermal system … will secure its place as the leading solution for commercial geothermal applications," while Fabricio Cesário of Eavor GmbH called the result "a blueprint for wider European and global rollout." Later in 2026, the technology went on to be named "Overall CleanTech Innovation of the Year" at the CleanTech Breakthrough Awards.

The honest caveat is that closed-loop geothermal is still young, and drilling deep wells is costly, so the economics must keep improving to compete broadly. But the prize is immense: clean, always-on power that does not care whether the wind is blowing or the sun is shining, drawn from heat that exists almost everywhere on Earth. If Geretsried is truly a blueprint, it points toward a future where reliable renewable energy is a matter of engineering, not geological luck.