He spent seven years inside the boiler room before he decided to give the building a brain.
Co-Founder & CEO, Runwise // New York City
In thousands of older American buildings, a boiler from the Nixon era still fires on a clock and a guess. It heats apartments that are already too warm, on nights the forecast already knew would be mild, while tenants crack windows in February to let the waste escape. Jeffrey Carleton built a company on that exact image - the open window in winter - and turned it into Runwise, a smart operating system for the buildings we already have.
Today Carleton is co-founder and CEO of Runwise, a New York company whose proprietary wireless sensors and cloud software now run in more than 10,000 buildings across roughly ten states. The platform watches temperatures in real time, reads the weather forecast, and decides when a boiler - or a cooling, electric or water system - actually needs to run. The result, by the company's count, is over $100 million in energy costs cut for around 1,000 customers, and a measurable dent in the carbon that buildings throw off.
In June 2025 he closed a $55 million Series B led by Menlo Ventures, a round that was twice oversubscribed and lifted Runwise's total funding to $79 million. The new investors read like a hedge against every part of the building stack: MassMutual Ventures, Nuveen Real Estate, Multiplier Capital and Munich Re Ventures joined returning backers including Soma Capital, Fifth Wall and Alumni Ventures. Carleton's framing of where the money goes is characteristically blunt.
Every building needs to be rebuilt with software, not bricks. That's what we're doing at Runwise.
Most proptech founders arrive from software and discover real estate later. Carleton went the other way. After a degree in business and managerial economics from Brown University, he spent seven years as General Manager of Beachlane Management, responsible for operations and energy across 150 multifamily buildings in New York City. That is not a slide in a pitch deck. That is 150 boiler rooms, 150 sets of tenant complaints, and a daily education in how much money a static thermostat can burn.
The buildings he managed were running on infrastructure designed in the 1960s and 70s - controls that could not see the weather, could not be reached from a phone, and could not be told to stand down on a warm night. The standard fix, ripping out and rewiring control systems, was expensive, slow and risky enough that most owners simply lived with the waste. Carleton co-founded Runwise with Lee Hoffman, a repeat entrepreneur whose earlier company Veri raised $8 million and exited to The Knot, and Mike Cook. The bet was that the upgrade did not have to be a renovation. It could be a sensor network installed in a single day.
"We're trying to hit these climate goals, yet right in our literal building we're throwing money away. Every time you run a boiler when it doesn't need to run, you're wasting money and you're producing carbon emissions unnecessarily."
The mechanics are deliberately undramatic, which is the point. A 100,000-square-foot building gets roughly 20 to 25 wireless temperature sensors. They report continuously to a central Runwise controller, which averages the readings against tenant preferences and a forward-looking weather model, then decides whether the boiler should fire at all. Mesh connectivity means no expensive WiFi overhaul - a detail that matters enormously to a cost-conscious owner deciding whether to say yes. Installation lands in a day. The savings, the company says, typically pay back the system in under five months.
That arithmetic is why the customer list reads the way it does: Related, Equity Residential, FirstService Residential, Rudin, LeFrak, UDR, Douglas Elliman and Akam on the real estate side, plus public heavyweights like the MTA, the Port Authority and National Grid. What began as a fix for overheating in winter has grown to cooling, leak detection and gas detection - the company's answer to a record-hot summer is the same sensor logic pointed at air-conditioning load.
Buildings are a bigger climate story than most people realize - and a bigger savings story.
For years the Runwise story was a winter story. The villain was the overheated apartment, the radiator that would not quit, the tenant prying open a window in January to make a too-hot room bearable. That is the waste Carleton watched accumulate across 150 buildings, and it is the waste the first version of the product was built to kill - a boiler that fires only when the building, and the forecast, agree it should.
But the same logic runs in the other direction. As CNBC reported in August 2025, record summer heat turned cooling into the new pressure point for commercial real estate portfolios, and Runwise pointed its sensor network at air-conditioning load the way it once pointed it at boilers. The platform now reaches across heating, cooling, electric and water systems - the building's whole metabolism rather than one organ of it. Carleton's pitch to owners does not change with the season: there is money leaking out of the building right now, and software can see it before a person can.
He has been clear that the next layer is artificial intelligence. As more buildings come online and more data flows back, Runwise plans to let AI continuously refine the control algorithms, so the system improves with every winter and every heat wave it weathers. The vision is less a gadget and more a learning loop - a building that gets smarter the longer it runs.
The Idea UnderneathAsk Carleton where this ends and the ambition gets bigger than thermostats. The aspiration is a connected cloud for buildings - the way Samsara built an operating layer for trucks and industrial fleets that other tools could plug into. There are roughly 12 million buildings in the United States and most of them still run blind. Runwise's plan is to add AI that keeps refining its control algorithms as more data flows in, so the system that saves a building money this winter is smarter the next.
It is a climate pitch and a cost pitch at the same time, which is exactly why it travels. An owner does not have to care about carbon to say yes to a five-month payback - and an owner who cares about carbon gets both. Carleton spent seven years watching money leave through cracked windows. He is now in the business of closing them, one boiler at a time, with software instead of bricks.
The $55 million Series B did not arrive because Runwise had a clever thermostat. It arrived because the company had quietly become a vertically integrated platform - it makes its own wireless hardware, owns the connectivity layer, and runs the cloud software on top, rather than stitching together someone else's parts. That control is what lets the system install in a day and behave predictably across thousands of very different buildings, from prewar walk-ups to commercial towers. Since its seed round, the company has grown roughly 30X, and Carleton has said it was tracking toward nearly doubling again.
The investor roster tells you who believes the thesis from which angle. Menlo Ventures led on the technology and scale story. Nuveen Real Estate and Fifth Wall bring the property world's perspective. MassMutual Ventures and Munich Re Ventures - an insurer's venture arm - sit close to the risk and resilience of physical buildings, exactly the kind of stakeholder that benefits when a building can detect a leak or a gas problem before it becomes a claim. That breadth is the quiet argument for Runwise: heating efficiency is the wedge, but the platform touches everyone who owns, insures, finances or lives in the building.
There is a market-size case underneath all of it. By the company's framing, building operations represent a $20 billion-plus opportunity, against a backdrop of roughly 12 million U.S. buildings still running on infrastructure that cannot see, think or be reached remotely. Carleton's contention is that none of those buildings need to be torn down to be modernized. They need an operating system retrofitted into the bones they already have. That is a far cheaper, far faster path to the same emissions targets cities keep setting and missing - and it is the path Runwise is selling.
What gives the argument weight is that it comes from someone who lived on the other side of the sale. Carleton was once the building manager getting pitched, the operator who had to weigh whether a control upgrade was worth the disruption. He knows precisely why owners say no - the cost, the downtime, the risk of touching a system that mostly works - because he used to be the one saying it. Runwise is, in a sense, the product he wishes someone had been able to sell him: cheap enough, fast enough, and reversible enough that the answer becomes yes. The company he runs is the answer to the frustration of the job he used to have.