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Another key detail is its cold-weather capability.
Photo Credit: BIWATT
In Augsburg, Germany, one homeowner built a house power system that operates entirely off-grid. 
While that’s impressive enough, the tech behind the project makes it one worth shouting about.
As battery maker Biwatt shared in a piece published in PV Magazine, the most unusual part of the project is the storage choice. 
Because the batteries were to be installed indoors in the basement, the homeowner opted for sodium-ion instead of a large lithium system, prioritizing safety while also weighing cold-weather performance and environmental impact.
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The home’s setup combines a 49-kilowatt-peak solar array with 270 kilowatt-hours of battery storage. Its hardware includes 60 Biwatt R2 sodium-ion battery units and four 12-kilowatt Biwatt H3 hybrid inverters, which together provide 48 kilowatts of inverter power for the house.
The design took shape after the homeowner asked Salzstrom, Biwatt’s local distributor, for an alternative to placing a large lithium-ion battery system inside.
Biwatt said its sodium-ion chemistry offers greater thermal stability and a lower thermal-runaway risk than lithium iron phosphate, helping address the homeowner’s concerns about an indoor battery installation.
Another key detail is its cold-weather capability. Biwatt says the R2 can keep operating at temperatures as low as minus-22 degrees Fahrenheit without auxiliary heating, leaving more of the stored power available for household use instead of warming the batteries.
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“You made a dream come true,” the homeowner was quoted as saying.
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Running a home off-grid means the system has to supply power through every hour of the day, including winter periods and stretches with limited sun. In this case, electricity produced during daylight is stored and used later.
The battery decision was not only about safety. The homeowner was also considering the materials footprint. 
💡Go deep on the latest news and trends shaping the residential solar landscape
Lithium extraction may require heavy water use and can disturb land. Biwatt said its sodium-ion batteries rely on widely available sodium and coconut-shell-derived hard carbon, a lower-impact materials path that matched the homeowner’s aim of building an all-green home energy system.
Even for people who never intend to go fully off-grid, safer and more adaptable battery technologies could make home backup power a more realistic option.
As battery choices continue to expand beyond traditional lithium, homeowners may gain more options tailored to safety, climate, and cost. 
Curating competitive bids is a big part of that. With EnergySage’s help, the average person can save up to $10,000 on solar purchases and installations, making it easier to evaluate whether solar and storage make financial sense.
EnergySage’s solar map shows the average cost of a home solar panel system in each state and outlines the incentives available there, helping readers get the best price for rooftop solar panels and access savings they might otherwise miss.
Adding battery storage to a solar setup is one of the best ways to protect your home during outages, save money on energy, and even move closer to going off-grid. If you want to compare your options, EnergySage offers information about home battery storage systems, including competitive installation estimates.
Many companies and engineers are working on solutions for everything from safer indoor batteries to more flexible home backup and a growing list of alternatives to lithium. Newer technologies could make resilient solar storage more realistic for homeowners who aren’t trying to live fully off-grid.
• Palmetto has begun offering backup batteries without upfront costs, lowering a major barrier for homeowners.
• Engineers are advancing water-based batteries for garages, highlighting safer alternatives to indoor lithium packs.
• Engineers testing iron instead of lithium are broadening the menu of safer storage chemistries.
• Researchers have created near-perfect battery technology from abundant materials, underscoring how fast storage chemistry is changing.
• A recycler’s reuse of discarded lithium cells has spotlighted the fire risks surrounding battery waste.
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© 2025 THE COOL DOWN COMPANY. All Rights Reserved. Do not sell or share my personal information. Reach us at hello@thecooldown.com.

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