The Merino heat pump is a single-room system, as opposed to the popular ducted and ductless whole-home systems. A key feature is that, unlike whole-home heat pumps, the Mono doesn’t require a large outdoor unit to move heat into or out of living spaces. Instead, it’s installed through the exterior of a building, and the portion that would normally live outdoors is tucked into the unit itself.

Merino is offering its heat pumps for a flat rate of $3,800, which — unusually — includes the cost of professional installation. A certified contractor can get the system up and running in under an hour, according to the company.

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The co-founders were largely inspired by an existing heat-pump design: packaged terminal heat pumps, Rau said. Commonly found in hotels and hospitals, these units combine all components in one container installed through a building’s wall.

Although this type of heat pump can cost less than $1,000 and is relatively simple to use in new construction, putting it in existing buildings typically requires cutting through load-bearing studs, Rau said. Contractors have to take special care to structurally reinforce the compromised wall, adding cost and complexity.

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The geometry of the Mono leaves studs intact. Installers drill two vents, each 6 inches in diameter, between the studs of an exterior wall. These holes allow the Mono to exchange thermal energy with the ambient air. What’s visible indoors is a sleek, white air handler.

Like other room heat pumps, the Merino units plug into a standard 120-volt wall outlet. At max, it can pull 900 watts and serve a 350-square-foot space, Rau said. Installing a flock of them can allow a home to avoid an expensive electrical service upgrade that a ductless system might incur, she added.

The unit is particularly well-suited to urban buildings with limited outdoor space and restrictive property rules, Rau said, such as historic homes, condos, and accessory dwelling units. The product is designed for mild and moderate climates like California’s. New York City, by contrast, is using cold-climate window heat pumps from Gradient and Midea to decarbonize public housing. And last year, Boston also contracted Gradient, paying $5,450 per heat pump.

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Merino already has its first retrofit project underway. Novin Development selected the startup to deploy its heat pumps in Civic Center Apartments, which will house low-income residents in Richmond, California, Rau said.