Closed-Loop vs. EGS — The Geothermal Technology Fork That Will Define the Next Decade

Fervo and Eavor both crossed the commercial threshold in 2025, but they represent fundamentally different bets on how geothermal scales. This analysis provides a five-dimension framework for matching technology to project context.

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Two Technologies, One Question

Two fundamentally different approaches to next-generation geothermal crossed the commercial threshold in 2025. Fervo Energy's enhanced geothermal system at Cape Station, Utah is scaling toward 100 MW, while Eavor Technologies' closed-loop radiator in Geretsried, Bavaria delivered its first electricity in December 2025. Both work, both are real, and they are not the same bet.

EGS fractures hot rock and circulates water through it, borrowing its engineering DNA from the shale revolution. Closed-loop seals fluid inside a pipe and extracts heat through conduction, more radiator than reservoir. They share a goal -- firm, 24/7 baseload power with zero combustion emissions -- but they diverge meaningfully on geology, risk, capital structure, and the type of offtaker they're best suited to serve.

The question is no longer whether next-generation geothermal works. Operators and investors now face a sharper question: which approach fits which project context, and where should capital flow? This analysis provides a framework for that decision.

The Numbers Behind the Noise

Global geothermal capacity is roughly 16 GW — less than 0.5% of total electricity generation. The U.S. Department of Energy estimates that the country alone has more than 300 GW of geothermal potential, but conventional hydrothermal resources — the fortunate locations where heat, water, and permeability naturally coexist — are concentrated in a handful of Western states.

Next-generation geothermal is designed to unlock it. EGS creates artificial permeability in hot, dry rock. Closed-loop bypasses the rock formation entirely. Both approaches could deploy geothermal anywhere with sufficient heat at drillable depth — a dramatically larger addressable market than the conventional resource base.

The economics are converging but haven't reached grid parity. Current EGS project costs run approximately $140/MWh, though recent power purchase agreements are reportedly pricing near $70/MWh (Cape Tryon estimate based on industry benchmarks), reflecting the gap between first-of-a-kind installed costs and forward pricing for repeat deployment. The DOE's Enhanced Geothermal Shot targets $45/MWh by 2035, while the National Laboratory of the Rockies projects $100/MWh under more conservative assumptions, with a demonstrated pathway to $64/MWh as the drilling learning curve steepens. Eavor's Geretsried project operates under Germany's feed-in tariff at roughly $270/MWh (EUR 250/MWh) -- a high number, but one that reflects the premium inherent in proving out a first-of-a-kind system rather than the technology's long-run cost structure.

What changes the comparison is firmness. Geothermal delivers power around the clock — it runs at 3 AM in January, not just on sunny afternoons. When you add the storage and firming costs required to make intermittent renewables dispatchable, the effective cost gap narrows or reverses. Google, Meta, and Microsoft are signing geothermal PPAs because their data centers need continuous power, and intermittent renewables plus storage now cost more than firm geothermal to deliver that profile.

Figure 1: Next-Gen Geothermal at a Glance

View interactive table

Recent capital raises confirm the trend. Fervo closed a $462 million Series E round in December 2025 and followed it with a $421 million non-recourse project loan in March 2026 -- a milestone that signals the transition from venture-backed technology risk to bankable project finance. Sage Geosystems raised $97 million in Series B in January 2026 with Ormat Technologies and Carbon Direct Capital co-leading. Combined with Eavor's EU Innovation Fund backing, more than $1.5 billion has been invested in next-generation geothermal since 2021. The question is now how to allocate capital across competing approaches.

The Technology Fork: Five Dimensions

EGS and closed-loop diverge on subsurface strategy, risk, cost structure, scalability, and geographic fit. Comparing them across these five dimensions clarifies where each has an edge and where the costs bite hardest.

1. Subsurface Strategy

EGS borrows directly from hydraulic fracturing: pump fluid into hot, impermeable rock to create fractures, then circulate water through the fractured zone to extract heat via convection. Fervo's key innovation has been applying horizontal drilling and multi-stage completion techniques from shale -- the same operational playbook that unlocked tight oil a decade ago -- to geothermal formations, achieving flow rates and thermal output that conventional geothermal wells could not approach.

Closed-loop bypasses the reservoir entirely. Eavor's system drills two vertical wells connected by horizontal laterals at depth, creating a sealed pipe radiator within the rock formation. Fluid circulates through the closed system, extracting heat via conduction through the pipe walls -- no fracturing, no reservoir creation, and no interaction with subsurface water or native rock permeability.

At Geretsried, Eavor proved what skeptics had questioned: a thermosiphon effect that circulates fluid without mechanical pumping, established within 30 minutes of startup. Eliminating the circulation pump removes parasitic power losses and simplifies the surface plant — a material advantage for operating economics.

EGS depends on geological favorability — you need hot rock with the right stress regime in a location where fracturing is technically feasible and socially permissible. Closed-loop can operate in any formation with sufficient temperature at depth, but that flexibility comes at a capital cost premium the technology hasn't yet worked through.

2. Risk Profile

The risk trade-off between the two approaches is relatively clean: EGS carries more subsurface and regulatory risk but benefits from a deeper and more battle-tested technology base. Closed-loop trades subsurface risk for engineering and capital risk -- the wellbores must be long, precise, and expensive, and the per-MW capital intensity remains higher at this stage of the learning curve.

3. Economics and Capital Structure

Fervo's drilling data traces a cost curve that any oil and gas operator will recognize. Per-well costs at Cape Station dropped from $9.4 million to $4.8 million across the first four horizontal wells, driven by a 70% reduction in drilling time. The 35% learning rate per doubling of wells mirrors unconventional oil's cost trajectory — and suggests current EGS costs have room to compress as deployment scales.

Cape Station Phase I is budgeted at approximately $6,000/kW, already approaching the DOE's 2030 target of $5,000/kW ahead of schedule.

Eavor's cost curve is earlier but steepening. The Geretsried team documented a 50% reduction in drilling time per lateral and a 3x improvement in bit run lengths over the course of the project, while their proprietary Rock-Pipe sealant reduced well construction costs by more than 40% compared to conventional cemented casing. Total project investment reached approximately $375 million (EUR 350 million) -- a first-of-a-kind capital premium that subsidizes every project that follows.

"Taking something that unlocked the shale revolution and making it work for hard rock was our whole thesis. The biggest expense in drilling is the time it takes to drill. The easiest way to reduce drilling costs is to drill faster." — Tim Latimer, CEO, Fervo Energy

EGS costs fall along a known drilling learning curve. Closed-loop costs are also drilling-dominated but require more total wellbore footage per MW, keeping per-meter costs above conventional directional drilling. The offset: once built, closed-loop has lower operating costs, and the thermosiphon effect eliminates pump power losses entirely.

4. Scalability and Deployment Speed

EGS reaches gigawatt scale faster. Cape Station Phase I targets 100 MW of grid power by October 2026, with Phase II adding another 400 MW by 2028. Baker Hughes is manufacturing five 60 MW steam turbines for the project — major OEM engagement that marks the start of EGS supply chain industrialization. The oil and gas drilling workforce transfers directly to EGS operations, a scaling advantage closed-loop lacks.

Closed-loop is further out. Geretsried is configured for 8.2 MWe and 64 MWth, and the technology requires extremely precise directional drilling with more total wellbore footage per unit of energy than EGS. Eavor's second loop began drilling in March 2026; the company must still prove repeatable unit economics before project finance opens up.

Closed-loop's advantage emerges in regulated, water-scarce, or urban environments where fracturing is prohibited or impractical. District heating and industrial process heat may be where closed-loop reaches revenue fastest, especially in Northern Europe where thermal energy commands higher prices than electricity and regulators favor non-intrusive subsurface technologies.

5. Geographic Fit

EGS needs high heat flow, favorable stress regimes, and water. The Western U.S. (Nevada, Utah, California) is the primary deployment region, with East Africa, Iceland, and parts of Southeast Asia offering similar geological profiles.

Closed-loop can deploy anywhere with sufficient temperature at depth — roughly 150°C or higher at 3-5 km. This opens regions that conventional geothermal and EGS cannot easily serve: the U.S. Midwest, Northern Europe, Japan, and South Korea, where geological or social constraints make reservoir stimulation impractical.

Sage Geosystems' "Pressure Geothermal" approach uses fractures connected to a single wellbore in a huff-and-puff cycle that harvests both heat and subsurface pressure. Meta has contracted 150 MW with Sage for data center power at a location east of the Rockies. The company closed $97 million in Series B funding in January 2026 with Ormat Technologies co-leading, and its first commercial plant is expected to come online later this year. Pressure Geothermal fits the sedimentary basins east of the Rockies where data centers concentrate — geology unsuited to pure EGS or closed-loop, but where demand for firm, zero-carbon power is highest.

The Decision Framework

Choose EGS when:

• The site has high heat flow and favorable stress conditions, particularly in Western U.S. geothermal fairways

• The project requires large-scale electricity generation, on the order of 50+ MW per site

• Water resources are available and there is a viable permitting path for subsurface stimulation

• The offtaker's primary objective is firm power at the lowest achievable cost per MWh

• The development timeline can accommodate 2-3 years of subsurface characterization and drilling before first power delivery

Choose closed-loop when:

• The site has adequate temperature at depth but unfavorable geology for fracturing, such as tight sedimentary formations or areas with seismic sensitivity

• Thermal energy is as valuable as or more valuable than electricity, as in European district heating or industrial process heat applications

• Induced seismicity is a non-starter due to regulatory constraints, political dynamics, or social license limitations

• The project requires predictable, engineered thermal output without the resource discovery risk inherent in reservoir-based approaches

• Deployment is planned in urban or suburban settings where environmental footprint and surface impact are significant considerations

  
  

Watch the hybrid space when:

• The target site is east of the Rockies with moderate heat flow in sedimentary geology

• A smaller-footprint, single-well solution is needed to fit the site or the capital budget

• The use case combines power generation with energy storage characteristics -- Sage's pressure approach offers dispatchability that neither EGS nor closed-loop currently matches

  
  

Key Takeaways

• EGS and closed-loop geothermal are complementary technologies that address different geologies, risk profiles, and end-use markets. The sector will support both, and the most informed capital allocators are already funding both.

• EGS has the faster path to grid-scale electricity and a lower near-term LCOE trajectory. If Cape Station Phase I delivers 100 MW to the grid by October 2026 as planned, EGS transitions from promising technology to investable asset class at utility scale. Fervo's drilling cost curve -- from $9.4 million to $4.8 million per well, with a 70% reduction in drilling time -- is the most important cost data series in geothermal today.

• Closed-loop's competitive advantage lies in predictability and environmental profile: no induced seismicity, negligible water consumption, and the ability to deploy in geologies and jurisdictions where EGS cannot operate. The thermosiphon demonstration at Geretsried resolves one of the technology's key skeptic questions around parasitic pumping power. Near-term economics favor heat markets, particularly in Europe where thermal energy pricing supports the current cost structure.

• The supply chain bottleneck differs by technology. EGS faces constraints in turbomachinery and surface equipment -- Baker Hughes turbine deliveries are the current chokepoint at Cape Station. Closed-loop faces precision drilling costs and the total wellbore footage required per MW of output. Both technologies draw from the same drilling workforce, and scaling that talent pool is a shared constraint.

• The optimal strategy is matching technology to site and offtaker, not picking a winner. Deploy EGS in Nevada, closed-loop in Bavaria. The fit matters more than the technology.