US enhanced geothermal systems (EGS) developer Sage Geosystems has completed more than 120 days of operation at its SMECI facility in South Texas, reporting low water losses and reservoir performance that it says matched or exceeded its operating objectives.
The facility began selling electricity in the second quarter of 2026 and has since been used to assess subsurface pressure response, injection and production behaviour, water retention, system efficiency and reservoir performance.
Sage reported water losses of less than 10% across multiple operating cycles. The company said the result indicates that most of the injected water remains within the engineered reservoir, allowing repeated production cycles without the high water losses that can limit EGS projects.
The operating data is now being incorporated into the design of Sage’s planned geothermal development at an Ormat site in Nevada. Sage also said its GeoTwin modelling system successfully predicted operating behaviour observed during the SMECI campaign, providing field data against which its subsurface models can be assessed.
The SMECI system uses pressurised water within an engineered subsurface reservoir. Rather than relying on naturally permeable geothermal formations, the approach is intended to create and actively manage a reservoir through controlled injection and production.
Sage plans to continue operating the facility while using the results to refine larger projects. The company is targeting water losses below 5% as its technology develops.
“Commercial geothermal isn’t just about creating a reservoir; it’s about creating one whose performance can be engineered, predicted, and consistent,” said Lev Ring, Sage’s co-founder, president and CTO.
The results provide operational data from a field-scale EGS installation, although larger projects will still need to demonstrate that the performance can be reproduced at commercial scale and under different geological conditions.
Sage said its next phase of development will focus on applying the SMECI data to project design, reservoir modelling and optimisation as it moves towards larger geothermal power plants.
