UL Solutions has introduced a dedicated testing and certification program for plug-in solar systems, often called balcony solar, marking an important step toward mainstream adoption of this technology in the United States. Until now, plug-in solar has lacked a clear, nationally recognized safety framework in the U.S., creating regulatory uncertainty for manufacturers, utilities, and consumers.

The new program establishes a formal pathway for manufacturers to demonstrate that plug-in solar products meet defined safety and performance expectations, addressing one of the main barriers to wider deployment.

What the New Certification Covers

The program is based on UL 3700, an Outline of Investigation specifically developed for interactive plug-in photovoltaic equipment and systems. It sets out construction, performance, and labeling requirements tailored to solar systems designed to connect directly to household electrical outlets.

Unlike traditional rooftop solar, plug-in systems are meant to be simpler and more accessible. However, that simplicity introduces unique risks, such as circuit overloads, accidental contact with live components, and unintended backfeeding of electricity into the grid. UL 3700 directly addresses these issues.

Certified systems must include features that reduce the risk of electric shock, ensure safe installation, prevent overloads, and control the direction of power flow. By doing so, the standard helps ensure that plug-in solar systems can operate safely within residential electrical environments.

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Expanding Access to Solar Energy

One of the most significant implications of the new framework is expanded access. Plug-in solar systems can be particularly relevant for renters and residents of multi-unit buildings who cannot install permanent rooftop systems. Certified products could also provide limited backup power for essential devices during outages, improving household resilience.

UL Solutions executives emphasized that the goal is not to replace traditional rooftop solar, but to complement it by enabling a broader range of consumers to participate in distributed energy generation.

Alignment With Emerging State Policy

The timing of UL 3700 aligns closely with recent and proposed state-level policy changes. Utah has already become the first U.S. state to allow plug-in solar systems up to 1.2 kW without requiring utility approval. Other states, including New York, Maryland, Minnesota, Pennsylvania, Vermont, Virginia, and New Hampshire, are considering similar measures.

By offering a clear safety benchmark, UL 3700 provides regulators and lawmakers with a trusted technical reference, helping reduce uncertainty around product approval, grid safety, and consumer protection.

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A Signal to Manufacturers and Investors

For manufacturers, the certification program creates a clear design target and accelerates go-to-market pathways. For investors and energy system planners, it signals that plug-in solar is moving from a niche concept toward a regulated, scalable category within the U.S. clean energy landscape.

As distributed energy systems evolve, UL Solutions’ move highlights how standards and certification can play a decisive role in turning emerging technologies into viable, trusted infrastructure for the energy transition.

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