On January 7, 2026, Constellation Energy closed its $16.4 billion acquisition of Calpine Corporation, creating the largest private-sector power producer in the United States — 55 gigawatts of combined capacity, the country’s biggest nuclear fleet stitched together with Calpine’s natural-gas turbines and one unusual asset that the press release referred to as the “crown jewel of geothermal energy.” That asset is a 45-square-mile patch of the Mayacamas Mountains north of San Francisco where 18 power plants sit on top of a 1.3-million-year-old blob of cooling magma, drilling holes up to 12,900 feet deep into a sandstone reservoir to capture the steam that rises through it. The complex is called The Geysers, which is a misnomer — there are no actual geysers, never have been — and it is the largest developed geothermal field on Earth. It has been generating commercial electricity since September 25, 1960, which makes it older than the Beatles’ first single. It currently produces around 725 megawatts of around-the-clock baseload power, which is enough to run a city the size of San Francisco, which is the city it largely runs.
It is also, in 2026, suddenly the most interesting piece of legacy infrastructure in the American energy system — because the AI build-out is consuming power faster than the grid knows how to supply it, every additional megawatt of AI computation requires roughly 1,000 metric tons of copper to deliver, the chips inside those data centers are running flat-out 24 hours a day, and “around-the-clock carbon-free firm baseload” is the rarest combination of words in the electricity business. The Geysers does it. Has done it. For 65 years. In Sonoma County. While almost nobody noticed.
What it actually is
The Geysers sits in Sonoma and Lake counties at the northern end of the Mayacamas range, about 75 miles north of San Francisco. Beneath it, a body of silica-rich magma intruded into the crust roughly 1.3 million years ago and never fully cooled. The rock above the magma — fractured sandstone and metamorphic graywacke — is hot enough to flash-boil any groundwater that reaches it, and the reservoir produces something extraordinarily rare in the geothermal world: dry steam. Most geothermal resources produce a wet mixture of brine and vapor that has to be separated, condensed, and processed before it can drive a turbine. The Geysers produces vapor-dominated steam at roughly 240 degrees Celsius that comes out of the wellhead ready to push a blade. The metallurgy that allows turbine blades to spin year after year in continuous high-temperature steam without failing is genuinely difficult engineering — not as exotic as the single-crystal nickel superalloys in a jet engine, but the same family of material science applied to a different operating envelope. There are only two large dry-steam fields known on the planet. The other one is at Larderello in Tuscany, which started commercial geothermal production in 1913 and inspired the entire global industry. Larderello is roughly a third of the size of The Geysers in terms of installed capacity.
The site covers 29,000 acres of mountain ridges threaded with pipelines, well pads, generating stations, and cooling towers venting white steam plumes that are visible from passing aircraft. There are 591 wells in total, 376 of them currently active, drilled in some cases more than two miles below the surface. The steam is piped — through insulated, above-ground steel lines that snake across the ridgelines for miles, an exoskeleton of metal threading through chaparral the way the steel pipes of the Paris pneumatic post network once threaded through a city — to a network of 18 generating facilities, where it spins turbines, gets condensed into liquid water in cooling towers, and is then re-injected back into the reservoir to keep the cycle running. The whole system runs at a capacity factor in the low-to-mid 50s, meaning it is generating actual electricity roughly 53 percent of the time it could theoretically be running — extraordinary uptime for a renewable resource, dramatically better than solar’s 25 percent or onshore wind’s 35 percent, and the entire reason every hyperscaler in California is suddenly interested in geothermal power.
The decline and the toilet-flush rescue
The Geysers nearly killed itself in the 1980s. The original 1960 plant — PG&E Unit 1, a modest 11-megawatt machine on Big Sulphur Creek — proved the concept, and over the next three decades the industry expanded aggressively, adding plant after plant, drilling well after well, pulling steam out of the reservoir faster than the slow trickle of rainfall could replenish it. Total installed nameplate capacity climbed past 2,000 megawatts. Then, by 1989, the steam pressure began to drop. Wells that had once roared started to wheeze. Production declined. Several plants ran at a fraction of nameplate. Calpine shut down Units 9 and 10 entirely in 2000 and 2001 because they couldn’t make money on the steam they were getting. The reservoir, it turned out, was a finite bathtub being drained faster than the spigot filled it, and the geothermal industry’s marquee American project was on a glide path to extinction. The Romans built aqueducts on the same assumption and ran them dry. The Mayan farmers cleared rainforest on the same assumption and watched their soil collapse. The Geysers’ operators built power plants on the assumption that the rain would keep up with the wells, and the rain did not.
The fix, when it came, was so unlikely that nobody outside the geothermal industry seems to know about it. In 1997, a consortium of operators — Calpine, NCPA, and Unocal at the time — completed the Southeast Geysers Effluent Pipeline (SEGEP), a 29-mile (later 40-mile) pipeline that carries treated wastewater from Lake County sewage plants up the mountain and pumps it down injection wells at a rate of about 9 million gallons per day. The water hits the hot reservoir, flashes to steam, rises through the production wells, drives the turbines, and gets condensed back into water in the cooling towers. The system was supplemented in 2003 by the Santa Rosa Geysers Recharge Project (SRGRP), a $250 million, 41-mile pipeline that climbs 3,000 feet through residential developments, vineyards, and the Mayacamas Mountain Sanctuary owned by the Audubon Society — which sued, then settled for $1.3 million — to deliver another 11 million gallons per day of tertiary-treated wastewater from Santa Rosa, Rohnert Park, Cotati, and Sebastopol. Total injection now runs around 20 million gallons of recycled water per day, which absorbs roughly 65 percent of the treated effluent from those communities and supports an estimated 77 megawatts of generation capacity that would not otherwise exist. Sonoma County’s flushed toilets are, in a quite literal sense, powering the data centers in San Francisco.
The SRGRP project worked exactly as designed. Steam pressure stabilized. Production declines slowed. The reservoir, which had been on a glide path to commercial death, is now expected to continue producing into the 2070s and possibly beyond. The closed-loop engineering — a system that runs on its own waste streams and produces its own inputs — is the same logic the ancient Persian qanats achieved through gravity 2,500 years ago and that Barcelona’s pneumatic waste network now achieves by piping garbage to a power plant at 70 kilometers per hour. The difference here is that the input is sewage and the output is gigawatt-hours, which is a thermodynamic transformation so unromantic that none of the parties involved is interested in publicizing it. A federal judge, two sanitation districts, and a geothermal company built the modern version of a closed-loop irrigation system on a hillside in California, and the customers paying premium rates for around-the-clock renewable electricity have, by and large, no idea.
The earthquakes the city tries not to mention
Injecting cold water into hot fractured rock makes the rock crack. The cracks make small earthquakes. The Geysers has, since the SEGEP and SRGRP pipelines came online, generated roughly 4,000 microearthquakes per year in the magnitude 1-to-3 range, with occasional events climbing into the magnitude 4 range that residents within a 20-mile radius can absolutely feel. The largest event attributed to Geysers injection was a magnitude 4.6 in 2006. None have caused significant structural damage. Almost all are tied directly, in the seismic record, to the volume and rate of wastewater injection in specific zones of the field. The operators monitor the swarms in real time and have learned over two decades to throttle injection at specific wells when activity climbs above thresholds.
The locals are not uniformly thrilled. “It’s Santa Rosa’s wastewater, and they don’t feel the earthquakes,” one Lake County resident told Scientific American in the early years of the SRGRP. The trade-off is asymmetric — the costs are borne by 500 year-round residents of the immediate area, the benefits flow to 725,000 households spread across five counties and increasingly to the AI training runs being conducted in server farms hundreds of miles away. It is the same distribution pattern that gives the Mumbai dabbawalas their famous reliability — costs concentrated in one place, benefits distributed across another — except that nobody is grumbling about the dabbawalas because their externalities are confined to the labor market they operate inside. The Geysers exports its electricity and imposes its tremors, the two flows do not move through the same zip codes, and the asymmetry is what makes mineral-rich communities carry the costs of energy systems consumed by people they will never meet.
The Constellation acquisition and the AI dimension
The reason any of this matters in 2026 in a way it did not matter in 2024 is that the calculus of electricity has changed. The Constellation-Calpine merger, which closed January 7, 2026, with a $16.4 billion equity price and a $26.6 billion enterprise value once Calpine’s debt was rolled in, was not really about geothermal — it was about Constellation building what its CEO Joe Dominguez has called a “one-stop shop” for the AI data center boom. The combined company has 32.4 gigawatts of nuclear, 26 gigawatts of natural gas, and the Geysers’ ~725 megawatts of geothermal — enough firm, around-the-clock generation to underwrite the kind of multi-year power purchase agreements that Microsoft, Google, Meta, and Amazon are now signing with anyone who can credibly promise to keep the lights on for a hyperscale training cluster. The nuclear side of the merged portfolio is the bigger story in absolute megawatts — Constellation is the country’s largest reactor operator at a moment when the uranium supply chain is scrambling to fuel a nuclear renaissance it was not prepared for — but the geothermal side is the more interesting one structurally, because it sits at the intersection of a 65-year-old operating asset and a brand-new demand vector. Constellation’s stock has nearly doubled since the deal was first announced in January 2025. Analysts are forecasting a 20 percent boost to 2026 earnings per share. The Department of Justice forced the divestiture of two Texas natural-gas plants — the Jack A. Fusco Energy Center near Houston and the Gregory Power Plant near Corpus Christi — to clear antitrust review, the first DOJ consent decree in a major U.S. electricity merger in fourteen years.
What this means for The Geysers is that, for the first time in its commercial history, the site is part of a company whose primary strategic question is “how do we sell more electrons to people running language models.” The answer for The Geysers itself is “we make more steam,” and that is exactly what is happening. Calpine’s North Geysers Incremental Development (NGID) project, which began phased completion in 2025 and is scheduled for full commissioning in June 2026, is drilling 11 new production wells and 2 new injection wells across four well pads in the northern portion of the field, using existing pipeline infrastructure to route the additional steam to nearby plants. The first 7 megawatts of incremental output came online in June 2025 and is being purchased by MCE, the Bay Area community-choice aggregator. The full 25-megawatt expansion will be online by mid-2026 — modest in absolute terms compared to a 1.5-gigawatt natural-gas plant, but each of those 25 megawatts produces emissions-free electricity at a capacity factor that no solar farm or wind project can touch, which is exactly what the data center buyers want.
The longer-term story, though, is that The Geysers is no longer the only geothermal game in town. Enhanced Geothermal Systems — the new class of next-generation drilling technology pioneered by companies like Fervo Energy and Sage Geosystems — uses horizontal drilling and hydraulic stimulation techniques borrowed wholesale from the fracking industry to create artificial geothermal reservoirs in hot dry rock formations that don’t have naturally occurring hydrothermal systems. The underlying technology is the same directional-drilling apparatus that revolutionized shale oil and that runs on a global supply chain of specialty metals and electronic components that overlaps almost completely with the supply chain feeding the energy-intensive industries on the other side of the meter. Fervo’s Cape Station project in Beaver County, Utah is scheduled to deliver its first 100 megawatts of commercial output in 2026 and ramp to 500 megawatts by 2028. The company went public on May 13, 2026 at $27 per share and closed its first trading day up 33 percent, raising $1.89 billion to fund construction. Google, Meta, and a half-dozen other hyperscalers have signed offtake agreements for the output. Fervo’s pitch — and it is a credible one — is that EGS can deliver geothermal power outside the small handful of geological accidents like The Geysers, which means a future in which geothermal might supply not 0.4 percent of U.S. electricity but a meaningful fraction of total demand. One projection from Project InnerSpace estimates that geothermal could cover 64 percent of AI data center energy demand by 2030 under aggressive deployment scenarios.
Geothermal is competing for the same data center power purchase agreements that the nuclear fusion industry is now chasing — Commonwealth Fusion’s SPARC, Helion’s commercial plant, TAE’s commercial program — and that conventional fusion still hasn’t delivered after 70 years of being thirty years away. The pitch for each technology is roughly identical: around-the-clock carbon-free firm baseload power at gigawatt scale. Geothermal’s advantage is that it works today, at this site, with this engineering, and has been working since 1960. Its disadvantage is that the resource is geographically constrained to a small number of places on Earth, and the new generation of EGS deployments has not yet proven that the constraint can be engineered around at scale. The fusion companies have the opposite problem — the resource is universal but the technology has not yet produced a single commercial kilowatt-hour.
What 2026 actually looks like up there
If you stand on a ridge in the Mayacamas in 2026 and look down at the steam plumes, what you are seeing is an industrial complex that has been continuously operating since the year John F. Kennedy was elected president, that has survived its own near-death from over-pumping, that recovered through a 41-mile sewage pipeline running uphill through wine country, that generates 4,000 small earthquakes a year as a side effect of that recovery, that supports roughly 300 Calpine employees and 150 contractors who live in Lake and Sonoma counties, and that has just been folded into the corporate balance sheet of the largest private power producer in the United States in a $26.6 billion transaction whose primary justification was the energy needs of artificial intelligence. The 18 plants stay in operation while individual wells are deepened, while injection rates are throttled to manage seismicity, while new pipelines are commissioned, while the corporate ownership above them changes — the same maintain-while-running discipline that keeps an 800-meter outdoor escalator moving through Hong Kong typhoon seasons or that keeps Manhattan’s 144-year-old steam grid heating skyscrapers whose architecture made conversion to other fuels economically impossible.
The whole system is, in the most literal infrastructure sense, a survivor — the kind of installation that was built in a moment of technological enthusiasm, declined into commercial near-obsolescence, retrofitted itself with an unlikely fix that almost nobody would have predicted, and now sits at the center of a strategic conversation about whether the growth in computing demand and the growth in electrified manufacturing can be supplied by an electricity sector that was, until very recently, planning for flat demand. The same survival logic applies to pneumatic networks under Berlin that have outlasted five regimes, to the single rotating boat lift in Scotland that revived a derelict canal network, and to the suspended monorail in Wuppertal that has been carrying commuters over a German valley since 1901. Infrastructure does not have to be efficient or fashionable or new to be valuable. It has to be there. The Geysers has been there for 65 years, in dry steam, beneath 591 wells, on top of a 1.3-million-year-old magma intrusion, powering a city full of people who do not know its name — and it has never been more economically valuable than it is right now, in the middle of 2026, with twenty-five new megawatts of capacity coming online, a new owner whose entire corporate strategy is built around selling firm power to hyperscalers, and a generation of competing geothermal technologies trying to do, somewhere else in the western United States, what the Mayacamas Mountains have been doing on their own, since 1960, for free.