A legislative change in Utah sparked a nationwide wave of interest in a new form of residential solar energy. In March of last year, the state approved the use of plug-in photovoltaic systems—compact solar panels that can connect directly to a standard household electrical outlet and help supply electricity to a home. The move was quickly echoed by dozens of other states. Often referred to as balcony solar because the systems can be installed on apartment balconies, the technology has since become legal in places including Colorado and Virginia. By July 2026, legislation supporting balcony solar had cleared one or both legislative chambers in states such as New York, New Jersey, and California.
The rapid expansion of balcony solar across the United States has outpaced the development of the regulations needed to ensure it can be deployed safely. Although one recently announced microinverter now complies with the newly established certification requirements, no solar panel has yet achieved those standards. According to Craig Morris, chief executive of the German plug-in solar trade association Bundesverband Steckersolar, the United States still faces a range of legal and engineering challenges before the technology is fully established. “If you get the law,” he said, “then your work begins.”
Morris is well acquainted with those challenges because Germany served as the proving ground for balcony solar. During the 2010s, innovators discovered they could use newly available microinverters—originally developed for larger solar installations—to convert electricity from a single low-cost panel into alternating current that could be fed into a household outlet. The technology became especially popular after Russia invaded Ukraine in 2022, when soaring natural gas prices drove demand for affordable clean energy alternatives. Today, plug-in solar panels are sold in German retailers such as Aldi and Ikea, and the country has installed more than 2 gigawatts of balcony solar capacity.
Germany completed its regulatory framework for balcony solar in December 2025, establishing rules to ensure these systems could safely send electricity back through household outlets and, when appropriate, into the power grid. Under German law, customers using balcony solar are not permitted to participate in net metering, which compensates consumers for exporting electricity to the grid, because such arrangements introduce significant uncertainty for grid operators. Morris said his association also worked with German firefighters to demonstrate that the technology does not present a safety hazard. In addition, German regulations provide protections for renters whose landlords object to visible solar panels for aesthetic reasons. Property owners must have a legitimate justification—such as planned balcony repairs—if they wish to reject a tenant’s request to install the systems.
Ken Boyce observed Germany’s progress from the United States. As vice president of principal engineering at UL Solutions, the organization responsible for developing testing and certification standards for numerous electrical technologies, Boyce now oversees work that includes balcony solar. He said the speed at which the technology spread in the United States caught him off guard. “That Utah legislation passed and we said, “Oh, how about that?” Soon afterward, Boyce and a team of engineers began developing a certification framework. By the close of 2025, UL Solutions had produced the initial structure for UL 3700, the organization’s proposed U.S. testing and certification standard for plug-in photovoltaic systems.
UL 3700 is intended to resolve a variety of safety concerns associated with plug-in solar technology. One of the most basic issues is that household electrical wiring was never designed for electricity flowing into an outlet from an attached plug. Unlike the plugs found on common household appliances, the connector on a solar panel may remain electrically live even after it has been unplugged, potentially exposing unsuspecting users to danger. Plug-in photovoltaic systems also feed electricity into a home's wiring after the circuit breakers and other overcurrent protection devices, preventing those safety systems from detecting the additional electrical load. Reverse electrical flow through a ground fault circuit interrupter (GFCI)—the protective device integrated into electrical outlets—could also interfere with the GFCI’s ability to function properly. “There’s this kind of insidious aspect to it,” Boyce said, “and now you’ve bypassed that protection that’s required to protect consumers from electric-shock hazards.”
According to Nadav Enbar, a program manager at the nonprofit Electric Power Research Institute (EPRI), these characteristics make plug-in solar panels fundamentally different from familiar household devices such as refrigerators or toasters. Even so, he argues that regulators should classify and treat balcony solar as an appliance. The technology’s greatest strength lies in its simplicity: owners can plug it in and begin generating electricity without obtaining approval from a utility, applying for permits, or upgrading their home's electrical system. That convenience, Enbar said, is a key reason the technology has the potential to expand solar adoption across many more households.
To address these concerns, UL 3700 establishes a range of technical requirements. Beyond specifying details such as insulation thickness, the standard requires manufacturers to mitigate known electrical risks through methods such as wiring designs that provide additional overcurrent protection or the use of GFCIs capable of handling electricity flowing in both directions. The standard also requires plug-in solar systems to shut down automatically during a local power outage. That provision responds to one of the primary concerns raised by electric utilities—that a system continuing to feed electricity onto the grid during an outage could endanger utility line workers.
Manufacturers are free to determine how they comply with UL 3700’s requirements. However, because both the standard and the technology are relatively new, no balcony solar panels have yet earned certification under it. Enbar pointed out that the certification requirements are demanding, and some may not currently be achievable. One example is the bidirectional GFCI disconnect, which has not yet become commercially available.
As a result, balcony solar currently exists in a transitional period. According to EPRI, with one recent exception, the systems currently being sold and installed in states such as Utah either have no certification at all or rely on electrical certifications that were created for products other than plug-in photovoltaic systems.
Another critical issue is ensuring that utilities are informed when customers install these systems. David Eisenhauer, representing the utility SoCal Edison, told IEEE Spectrum that although the company supports customer access to plug-in solar technology, “it’s really important that customers notify us before they start to think about or install plug-in or balcony solar. That’s going to help us ensure that they’re installing certified equipment, help us track connections so that we can balance and operate the grid.”
Achieving that level of transparency may prove challenging. Research conducted by EPRI indicates that even in Germany, the world's leading balcony solar market, unregistered systems outnumber officially registered ones by a ratio of two to one. Some consumers prefer to avoid the extra effort involved in registering their systems, while others, Morris said, may deliberately choose not to publicize their plug-in photovoltaic installations or alert their landlords. As the number of unregistered, or “guerilla,” solar installations is expected to increase, the technology must be designed to operate safely under all circumstances, regardless of how many people install solar panels on apartment balconies or in their backyards.
The article was updated on 21 July 2026 to note that a microinverter announced while the reporting was underway does, in fact, comply with the UL 3700 standard. The correction was made after reader Stephen Mayer identified the oversight.
Originally reported by IEEE Spectrum on Jul 20, 2026.
