Fewer Deals, Bigger Tickets
According to Fintrx's exclusive readout to CNBC, family offices notched 42 direct investments in September versus 52 the month prior. Even so, the money didn't sit idle. These investors still leaned into a smaller set of oversized rounds.
Hillspire, the personal investment arm of former Google CEO Eric Schmidt, joined a Series D for Mistral totaling three billion euros, which translates to roughly $3.4 billion.
Stanley Druckenmiller's Duquesne Family Office appeared in two large financings: $500 million for Fab2 and $250 million for Precision Neuroscience. Fab2's specialty is building smaller-scale semiconductor fabs, while Precision Neuroscience designs brain implants that read neural activity so people can control digital devices.
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Clean Energy: Mazama's Heat Play
Clean-energy startups continued to draw this crowd, accounting for five of September's transactions. One standout was Mazama Energy. John Arnold's Centaurus Capital and John Doerr's family office co-led a Series B worth $135 million for the three-year-old geothermal company, with participation as well from Bill Gates' private venture capital firm. Both Arnold and Doerr have backed multiple clean-energy bets this year.
Mazama's approach is straightforward physics, heavy on engineering: drill into ultra-hot rock, circulate water through engineered fractures, bring that heat topside, and turn it into carbon-free power. The company says the setup produces more energy per well, helping cut power costs. In 2025, at its Oregon pilot, Mazama hit rock measuring 629°F, a mark it claims is the highest temperature ever recorded for an engineered geothermal system. The company adds that the Oregon site can already produce 10 gigawatts of energy.
Its temperature is proven. It is an engineering challenge."
What This Means For Your Portfolio
September's pattern is clear: fewer swings, bigger cuts. Family offices concentrated into massive AI, chips, neurotech, and geothermal rounds, and they favored teams showing real-world progress. For everyday investors, the signal is where patient private money is clustering right now and the kinds of milestones that turn experimentation into major checks.
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