Rapid Shutdown Devices and Safety in Commercial Solar

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Solar Inspection Data Links Rapid Shutdown Devices to Safety Risks

HelioVolta reports that critical safety issues are 66% more likely to occur in commercial solar systems with rapid shutdown devices

CARSLBAD, CA – March 17, 2026 – HelioVolta, an independent provider of field inspections and technical services for solar and energy storage projects, today announced the release of a new report, “Unintended Consequences: Rapid Shutdown Devices and Safety in Commercial Rooftop Solar Systems”.

The report urges solar asset owners and investors to reconsider module-level rapid shutdown devices (RSDs) for code compliance in commercial rooftop systems, citing data linking the technology to more than 74 high-risk reliability issues and thermal events since 2021.

RSDs are a type of power electronic device that performs one PV system function: reducing the voltage of PV modules to meet safety requirements in the National Electrical Code (NEC). Unlike power optimizers or microinverters, which offer performance and monitoring benefits alongside rapid shutdown capability, RSDs provide no additional system value. Findings are based on HelioVolta's field inspections of more than 500 commercial rooftop PV systems and industry research.

“Installing and maintaining safe PV systems is the best way for solar companies to protect first responders,” commented Dennis O’Neil, Asst. Battalion Chief (Ret.) of the California Department of Forestry and Fire Protection. “Failure-prone solar equipment puts firefighters at risk and is frankly unacceptable.”  

Findings from the report include:

• HelioVolta identified 21 rooftop fires caused by RSDs from 2021 to present through onsite inspections, technical consulting, and industry research.
• Rooftop PV systems with RSDs are 66% more likely to contain critical issues than those without any type of module-level power electronic devices (MLPE). Critical issues require immediate de-energization and remediation due to safety risks.    

“RSDs are often deployed to meet rapid shutdown requirements in the National Electrical Code, which were implemented with the best of intentions to protect first responders,” said Ryan Mayfield, an expert on electrical codes and standards. "It's important that codes and standards evolve with the industry to provide the best solutions for safe and reliable PV installations."

HelioVolta's report raises the question of whether the NEC’s rapid shutdown requirements unintentionally increased overall safety risks for commercial rooftop solar assets by triggering the widespread deployment of complex power electronic devices in concealed and largely unserviceable rooftop locations.

“Faulty RSDs are operating on buildings across the US, unintentionally putting people at risk. As these devices age, worst-case scenario failures are more likely to occur,” said James Nagel, CTO of HelioVolta. “No one wants to acknowledge safety risks hidden in solar portfolios, but we can only eliminate the dangers of RSDs with transparent, informed technical discussions.”

For asset owners and operators already managing systems with RSDs, the report acknowledges that options are limited due to the insurance impacts of code non-compliance and the high cost of retrofits. HelioVolta recommends proactive O&M measures for RSD-equipped portfolios, including annual visual and thermal inspections and remote monitoring for voltage imbalances. Owners should also explore converting RSD-equipped projects to UL 3741 for code compliance without MLPE, a viable option for system configurations with approved equipment.

“Our goal is not to promote a single technology pathway for PV systems,” commented David Penalva, CEO of HelioVolta. “It is to help the industry build safer, more reliable systems that benefit everyone. It’s what every community deserves.”

HelioVolta calls on solar professionals with RSD safety concerns to submit public input to the National Fire Protection Association(NFPA) as the NEC continues its code development cycle, and to report RSD-related safety incidents to HelioVolta to support the development of a national database.