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These net-zero, backyard tiny houses generate extra power to help pay for themselves

Equipped with solar panels and batteries, Cosmic’s accessory dwelling units, or ADUs, can send extra power to the main house, an electric car, or even back to the grid.

These net-zero, backyard tiny houses generate extra power to help pay for themselves
[Photo: courtesy Cosmic]

A new design for an all-electric backyard house comes with extra-large solar panels and batteries that can make and store more power than the tiny home actually needs—allowing the unit to help bring renewable energy to the main house on the lot and begin to pay for itself through savings on energy bills.

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[Image: courtesy Cosmic]
Cosmic, the startup building the tiny houses, wants to tackle two challenges simultaneously. The U.S. needs to build millions of homes—6.8 million units, by one estimate—to deal with the housing shortage that’s helping push house prices and rents higher; tiny backyard houses can help fill part of the gap by creating new rentals. Homes are also a major source of carbon emissions. The nonprofit Rewiring America estimates that switching everything in homes to run on electricity, from furnaces and stoves to a household’s cars, could address around 40% of the country’s emissions.

[Photo: courtesy Cosmic]
“The construction industry is not in a position to really tackle the [climate] emergency,” says Cosmic founder Sasha Jokic. The industry is also struggling to address the housing shortage; traditional construction, with each home built as a one-off design, is expensive and hard to scale up quickly, and in many areas, there’s a shortage of construction workers. Like some other startups building backyard houses or “accessory dwelling units” (ADUs), Cosmic uses a prefab design that can help lower costs and speed up construction by using standardized parts, though each home is customized for the buyer. It also uses an all-electric, efficient design and renewable energy to make it “net zero” for operational energy, meaning that the homes can generate at least as much energy as they use each year.

[Photo: courtesy Cosmic]
The tiny houses, which start at 350 square feet, use a standardized frame that includes built-in solar power and batteries, along with a built-in roof, floor, and mechanical, electrical, and plumbing systems. Jokic calls it a chassis, comparing it to the designs that some car companies are using to build batteries into the structure of an electric vehicle. Other building elements, including walls and windows, are designed to be precut in the factory and manually installed onsite.

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[Photo: courtesy Cosmic]
A lithium-ion battery stores energy from the solar panels on the roof and can send extra power to the main house or an electric car, or even back into the electric grid. The house also uses a heat pump, and stores heat in a system with hot and cold water tanks that can provide heating and cooling on demand.

[Photo: courtesy Cosmic]
The startup, which is currently working at the Autodesk Technology Center in San Francisco—a residency program for companies innovating in design and construction—has built one prototype and will begin producing its first homes for sale this summer. The company is experimenting with new financial models; it plans to offer both an option to buy a backyard house outright, starting at $190,000, and an option to buy the home separate from the “energy pack.” The second option, starting at $150,000, means that Cosmic would still own the renewable energy infrastructure and the extra power generated; residents would get free power for the backyard house and a discount on energy for the main house. “What we are trying to do here is really eliminating and absorbing the ‘green premium’ on energy production at home,” Jokic says.

[Photo: courtesy Cosmic]
The company is starting to work first in California where state laws, and extra support from cities like Los Angeles, have made it easier for homeowners to build backyard homes. (While some states have followed suit, others lag behind; and many cities in other parts of the country still don’t allow ADUs, or they require expensive and complex permits.) California now estimates that it needs to build 2.5 million homes by the end of the decade; in one older estimate, the McKinsey Global Estimate suggested that the state could add nearly 800,000 new units through backyard homes.

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[Photo: courtesy Cosmic]
As Cosmic scales up, Jokic says, it wants to bring down the cost of its ADUs. But the startup also wants to use the same basic approach to build larger single-family homes and then multifamily buildings, from duplexes and triplexes up to larger apartment buildings. “I think the end game for this company is the multifamily homes up to 15 units,” Jokic says. “We strongly believe that’s going to be the future in American cities—the ‘missing middle.'” Last year, California passed new laws that allow multifamily buildings on single-family lots, another way to help fill the housing gap.

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About the author

Adele Peters is a staff writer at Fast Company who focuses on solutions to some of the world's largest problems, from climate change to homelessness. Previously, she worked with GOOD, BioLite, and the Sustainable Products and Solutions program at UC Berkeley

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