Hoymiles Launches US Market’s First UL 3700-Compliant Plug-In Solar Microinverter

Hoymiles has launched the HiFlow Pro, marking the debut of the first plug-in solar microinverter in the United States to meet the newly established UL 3700 safety standard. This development could pave the way for widespread adoption of “balcony solar” systems among renters and apartment tenants who cannot install traditional rooftop solar panels.

The HiFlow Pro microinverter allows users to feed solar energy directly into their homes using a standard household electrical outlet. While plug-in solar setups have existed for years, safety concerns have historically limited their legal adoption in the US. The introduction of the UL 3700 standard in December 2025 established the first formal safety framework in North America specifically designed for plug-in photovoltaic energy systems.

A primary safety concern with plug-in solar systems is the risk of sending power back into the utility grid during a power outage. If a system continues to export electricity when the grid is down, it poses a severe electrocution hazard to utility line workers attempting to restore service. The UL 3700 standard addresses this by requiring built-in mechanisms to prevent accidental overloads and instantly disconnect the system from the grid during an outage.

According to a report by Electrek, several US states have already enacted legislation to permit plug-in solar technology, while others are currently debating similar measures. In Europe, balcony solar has experienced a massive boom due to streamlined regulatory frameworks and simplified plug-and-play standards. The US market has remained more restrictive due to complex local building codes and utility interconnection requirements.

While a plug-in solar system is generally not powerful enough to run an entire household, it offers a practical way to offset daily electricity consumption. By lowering the barrier to entry, certified devices like the HiFlow Pro allow apartment dwellers and renters to participate in the transition to renewable energy without the high upfront costs or permanent modifications associated with traditional rooftop installations.