The Two-Phase Cooling Era is Upon Us
Interview with Josh Claman of Accelsius
Episode Overview:
Josh Claman, CEO of Accelsius, has a simple thesis: every major industrial cooling system on earth — your car, your home air conditioner, every power plant — runs on two-phase physics, and data centers are next.
Accelsius recently raised a $65 million Series B — an unusual round by Claman's own description, structured entirely around strategic partners. Johnson Controls, with over a century of two-phase cooling experience, led the round; Legrand, a powerhouse in data center power infrastructure, followed on.
Key takeaways from the interview:
• Two-phase cooling is not a speculative bet — it’s an engineering inevitability. Your car, your home air conditioner, industrial power plants — they all use two-phase cooling.
• The AI infrastructure build-out has been a massive capital deployment in search of a profit pool that nobody has actually located yet.
• Accelsius is a picks-and-shovels play, which insulates it from the macro uncertainty around AI monetization.
Full Episode:
Full Audio:
Full Transcript:
The Two-Phase Cooling Era Is Upon Us
Josh Claman, CEO, Accelsius
Josh Claman: Accelsius does advanced liquid cooling for the data center. We use two-phase physics to carry the heat off in a very efficient way.
What trend or indicator will you be watching most closely in 2026?
Josh Claman: It seems a little self-centered, but I’ll be looking for a tipping point from single-phase water to two-phase cooling in the data center. We think it’s going to be the dominant architecture in the next several years. We look forward to seeing some indications of that.
For somebody who doesn’t understand — a brief explanation of that transformation from one standard to another.
Josh Claman: Data centers have a challenge with cooling. They’re moving from air cooling — just forced air over servers — to liquid cooling, which typically means a fluid goes over a plate that’s directly on top of the chip. The difference with single-phase, which was the first mover in the industry, is that it pumps water over that chip with no phase change. It carries the heat entirely through convection.
We do two-phase cooling: we pump a refrigerant over the chip and orchestrate a phase change. We go from fluid to vapor, and it’s that physics that carries off a huge amount of heat energy very efficiently. It has other benefits as well. That’s the fundamental difference.
What are the greatest unknowns in digital infrastructure in 2026?
Josh Claman: I think there’s a collection of them. From an economics standpoint, there’s a lot of investment in AI infrastructure. How is that going to pay off? What’s the real return on investment? How do you differentiate one LLM from another? How do you monetize these things effectively? Where is the power going to be in AI — is it going to be curated, very focused applications around pathology, law, diagnostics? Or is it going to be broad, with these large LLMs? Where is that profit pool going to end up?
I think this year we’ll see some indication of that. Over the last couple of years we’ve seen an aggressive build-out of infrastructure — almost with a hope and a prayer that we’ll find this profit pool. I’m looking forward to seeing how that advances this year.
What kinds of inbound calls are you getting from customers or investors? Any recurring themes?
Josh Claman: We just closed our Series B, which was very successful. We get a lot of inbound because I think the industry has come to the conclusion that, like most industrial sectors, you’ll go from single-phase to two-phase. Your car, your home air conditioner, industrial power plants — they all use two-phase cooling. There’s a general consensus among people who know the space that this is going to happen.
So we get a lot of excitement from investors: you’re the leader in two-phase cooling in the data center, we want a part of that, or at least we want to understand what your play is.
What makes you bullish to be part of the digital infrastructure opportunity going forward?
Josh Claman: I think it’s a revolution like we’ve never seen before. We can talk about potential bubbles, technology being overhyped, uncertainty around where monetization is going to occur most effectively — but something big is happening, and it’s really fun to be on the ground floor of that.
We’re kind of a picks-and-shovels play. Everyone’s going to need infrastructure, so we don’t have to worry as much about those macro issues. The overall sector, I think, will see growth, investment, and return that we haven’t really seen before in the history of modern business.
Anything you’ve been thinking about lately that people with an interest in this space should understand?
Josh Claman: I think it’s really our core technology. What we often say is: our architecture is better now and probably required in the future. We’re focused on creating a broad product line that can handle multiple use cases. We can handle very large thermal capacities. We can scale this technology out. That’s really what we’re focused on.
