How Quilt solved the heat pump’s biggest challenge

Smart home startup Quilt introduced a three-zone heat pump on Tuesday that promises to maintain efficiency even in the kinds of demanding conditions that stymie traditional incumbents.

The three-zone unit does what it says on the label: one outdoor unit is now capable of driving three indoor heads, as they’re known in the HVAC world. It’s a product that will make large installations simpler and cheaper while minimizing the footprint outside the home, and it’s key to the startup’s plans for expansion, which were recently turbocharged by a $20 million Series B focused on expanding sales.

But the real story is how Quilt developed the new product.

Since its founding, Quilt has prided itself on the amount of data it collects from its heat pumps. Not only are they internet connected, they’re also laced with more sensors than typical heat pumps. 

By analyzing that data, Quilt engineers have been able to do things that other companies have not. In September, for example, they shipped an over-the-air update to heat pumps in people’s homes that unlocked an additional 20% capacity, which could be directed toward either one or two zones. With the free update, people could be more comfortable during heat waves and cold snaps. 

The team also used the data to develop the new three-zone unit and, in the process, solve a vexing challenge that many competitors face.

Like all heat pumps, multi-zone units work best when they’re run at variable speed — that is, when heating or cooling demand is low, the compressor runs at a lower speed to deliver only the amount of heating or cooling that’s needed. 

But there are limits to how low they can operate. Compressors become less stable at low speeds, making them harder to control. Matthew Knoll, co-founder and CTO at Quilt, compares it to driving a car a low speeds. Maintaining an even 70 mph is easier than a steady 11 mph. “It’s a little harder,” he said. 

To compensate, most systems stop the compressor at a certain point, sacrificing some efficiency and comfort in the process.

Quilt, though, was able to draw on data collected from the thousand or so units already installed in people’s homes and businesses, giving them insights into how the systems were operating in the real world.

“The way most systems are developed, they’re tested in a lab under a couple scenarios because testing’s expensive. And you end up with kind of a you know an average product,” Knoll said. 

“We have a thousand units out there in many different climates, and if we see something, we can look at it across a bunch of different units to understand if there’s room to optimize or if we’re seeing a problem in a corner case,” he said

The company also uses a larger copper coil than many competitors, which allows it to spec a smaller compressor. That combination, along with some other tweaks to the design, allows Quilt to deliver nearly 90% of its rated capacity (27,000 BTUs) at -13˚ F (-25˚ C) without sacrificing low-demand performance or efficiency. Quilt says it’s the most efficient three-zone mini-split on the market.

To save power, each indoor head can be controlled individually, supplying as little as 2,210 BTUs of heat or 1,570 BTUs of cooling. If heating or cooling isn’t needed, refrigerant still flows through the lines like it does in other heat pumps. But thanks to the outdoor unit’s low-speed performance, it only releases around 300 BTUs of heat in heating mode. That’s about as much heat as a grown adult throws off.

Where does Quilt go from here? Knoll wouldn’t comment on future plans other than to say that Quilt “wants to be able to have a solution for all homes.” More products are coming, and it’s likely that reams of data will help lead their development.