Vienna’s Geothermal Testing Beats Expectations

A joint geothermal initiative in Vienna’s Aspern district has surpassed initial performance projections, paving the way for a massive expansion of sustainable district heating in the Austrian capital. Spearheaded by local utility Wien Energie and energy firm OMV, recent test drilling indicates the city’s underground resources are hotter and more abundant than previously thought.

During a functional test conducted in the fall of 2025, engineers extracted formation water from roughly 3,000 meters below the surface before reinjecting it underground. The results were highly encouraging:

1. Higher Temperatures: While pre-drill estimates anticipated water temperatures around 100°C, the test measurements reached a peak of 104°C.
2. Strong Flow Rates: The well demonstrated a robust flow rate, confirming the long-term productivity and stability of the subterranean reservoir.
3. Increased Capacity: Thanks to the hotter water and strong flow, the facility’s thermal output could jump from the originally planned 20 megawatts (MW) to as much as 25 MW.

As a result of this boosted capacity, the Aspern plant is now projected to provide sustainable hot water and heating to roughly 25,000 Viennese households—an increase of 5,000 homes over early estimates. Crews also successfully analyzed the water’s chemical makeup, a crucial step for finalizing the facility’s safety protocols and engineering design.

With the testing phase complete, project leaders are moving into the detailed planning and bidding stages for the surface infrastructure over the coming months.

Projected Timeline:

1. Early 2027: Construction on the Aspern plant begins.
2. Early 2029: The facility officially begins operations.

This Aspern facility serves as the foundation for the joint venture between OMV and Wien Energie. The partnership has ambitious long-term plans for the city, aiming to construct up to seven deep geothermal facilities in Vienna. Boasting a combined capacity of 200 MW, this network of plants could eventually supply green heat to 200,000 local homes.

According to Wien Energie CEO Sascha Zabransky, the Aspern plant will act as the blueprint for the city’s geothermal rollout. The utility’s ultimate goal is for deep geothermal energy to supply roughly 25% of Vienna’s entire district heating network by 2040.

To support this aggressive shift away from fossil fuels, Wien Energie has committed €3.2 billion toward broader energy transition initiatives by 2030. Approximately €1 billion of that budget is specifically earmarked for decarbonizing the city’s district heating system.

Regional Energy Transition Focus at Go Net Zero Energy

These will be key talking points at the upcoming Go Net Zero Energy summit. The premium regional forum brings together European energy operators, utility directors, and policymakers to dissect the infrastructure frameworks and balancing technologies driving Central and Eastern Europe toward a climate-neutral reality. To view updates on next years edition, check out the summit website