A small solar device that draws power through a standard household outlet is now available in the United States with a nationally recognized safety certification for the first time. Hoymiles released its HiFlow Pro microinverter last week, and it is the first product in the country to conform to UL 3700, a safety standard for plug-in photovoltaic energy systems adopted in December 2025.
According to a report by Engadget, the technology is sometimes called balcony solar because it is small enough to mount on an apartment balcony. A few states have already passed laws permitting the technology, and several others have proposed measures to allow it. The new federal standard may accelerate that process by giving regulators, utilities, and consumers a shared baseline for safety.
The central safety concern with plug-in solar is what happens during a power outage. Because these devices push electricity into a socket rather than drawing it out, there is a risk that power could flow back into the grid while crews are working to restore service. That would put repair workers in danger. UL 3700 standardizes the features that prevent accidental overloads and backstop that specific risk, among other safety concerns.
The devices are not capable of powering an entire apartment. Their value is in reducing how much electricity a household draws from the grid, without requiring a full rooftop installation or ownership of the property. For renters and apartment dwellers who have had no practical path to solar energy, plug-in microinverters represent a smaller, more accessible entry point.
The availability of a product that meets a national safety standard matters because it expands the potential market. Before UL 3700, there was no agreed-upon benchmark in North America for this category of product. That made it harder for states to write permitting rules and harder for consumers to know what they were buying. A certified product changes that calculation for regulators and buyers alike.
