Electrical Hazards and Safety Controls for Solar PV and Battery Storage Systems

Why Do Solar PV and Battery Systems Require Special Safety Controls?

Solar PV and battery storage systems require specialized safety controls due to their unique operational characteristics. PV modules generate DC (direct current) electricity whenever sufficient light reaches them, which continues during daylight hours. Opening an AC disconnect may not eliminate DC voltage, leaving hazardous energy present. Batteries contain both stored electrical and chemical energy that persists even when connected equipment is switched off. Multiple energy sources may feed the same installation, creating complex hazard scenarios. DC arcs can remain sustained and are difficult to interrupt compared to AC systems. Automatic controls, inverters and backup circuits can create unexpected energization. Battery faults may escalate from overcharging or internal defects to thermal runaway—a self-accelerating process in which heat generated inside a battery cell causes further internal reactions, increasing temperature, pressure and fire risk. For an overview of the full range of hazards solar workers face, see OSHA's green jobs solar energy safety hub.

Key Definitions:

• PV: Photovoltaic
• BESS: Battery energy storage system
• BMS: Battery management system
• PCS: Power conversion system

What Are the Most Common Solar PV Electrical Hazards?

Electric Shock and Electrocution

Workers can be exposed to dangerous DC voltages through damaged DC cables, exposed conductors, incorrect polarity connections, wet conditions, defective connectors, and inadequate isolation. Contact with energized components in inverters, combiners boxes, and disconnects poses additional shock risks. OSHA identifies electric shock, burns, electrocution and arc flash as important solar-work hazards that require comprehensive protective controls.

DC Arc Faults and Arc Flash

An arc fault is an unintended electrical discharge caused by damaged or loose connections between conductors. An arc flash is a rapid release of thermal energy capable of causing severe burns, pressure waves, and equipment damage. These hazards arise from loose or mismatched connectors, poor crimping practices, damaged cable insulation, incorrectly rated switches, and high-resistance connections. Workers performing tasks inside combiner boxes, inverters and switchgear face elevated arc-flash risk.

Ground Faults, Overcurrent and Reverse Polarity

Insulation failures, wiring mistakes and inadequate overcurrent or ground-fault protection can cause electric shock, fire, equipment damage, and create unexpected conductive paths. These faults may trigger uncontrolled fault currents or allow leakage current to energize frame ground.

Rooftop and Environmental Hazards

Electrical risks are compounded by water ingress into cable terminations, UV-degraded insulation, lightning and surge exposure, extreme heat, roof fall hazards, and restricted emergency access on rooftops. These environmental factors accelerate degradation and create additional injury scenarios.

What Are the Main BESS Electrical and Fire Hazards?

Stored Energy and Short-Circuit Current

Battery systems can deliver extremely high fault current during accidental terminal bridging, conductive tool contact, incorrect battery connections, damaged busbars, or failure to isolate parallel battery strings. These faults produce instantaneous thermal energy and arc hazards.

Thermal Runaway

Thermal runaway is a self-accelerating process in which heat generated inside a battery cell causes further internal reactions, increasing temperature, pressure, gas production and the possibility of fire propagation. Possible initiating factors include internal cell defects, mechanical damage, external heating, overcharging, short circuits, cooling-system failure, BMS sensor failure, and manufacturing defects. UL 9540A is a recognized test method for assessing thermal-runaway fire propagation in battery energy storage systems.

Fire, Explosion and Hazardous Gases

Some battery failures produce flammable gases, toxic or irritating decomposition products, smoke, and pressure accumulation. Re-ignition risks persist even after apparent extinguishment. Proper ventilation, monitoring systems, and isolation devices are essential controls.

Battery Electrolyte and Chemical Exposure

Different battery chemistries present distinct hazards. Lithium-ion batteries involve organic electrolyte risks, while lead-acid batteries produce hydrogen gas and corrosive sulfuric acid. Manufacturer controls and chemistry-specific PPE requirements must be implemented.

How Should HSE Officers Assess Solar and Battery Risks?

A five-step risk assessment process is recommended:

1. Define the task and system boundaries
2. Identify every AC, DC, battery and backup-energy source
3. Identify who could be harmed and how
4. Evaluate likelihood, severity and existing controls
5. Assign additional controls, responsible persons and review dates

The assessment should cover installation, commissioning, routine operation, fault finding, cleaning, maintenance, emergency response, and decommissioning activities. Professionals responsible for these assessments can develop practical electrical hazard-control skills through formal electrical safety training, including hazard recognition, isolation principles and safer working practices.

What Should Be Checked During a Solar and BESS Inspection?

Regular inspection and preventive maintenance prevent hazards from escalating and extend system life. Key inspection points include:

• Damaged, loose or overheated connectors
• Incorrect or mixed connector types
• Cable abrasion, UV degradation and poor routing
• Water ingress into terminations or junction boxes
• DC-isolator condition and mechanical operability
• Combiner-box and inverter overheating
• Grounding and bonding continuity verification
• Warning labels and emergency system diagrams
• Battery swelling, leakage or corrosion indicators
• BMS alarms and abnormal temperature trends
• Ventilation and cooling-system operation
• Fire-detection and automatic shutdown-system functionality
• Unauthorised system modifications or unauthorised repairs

Testing intervals should follow local electrical codes, manufacturer instructions, risk assessment findings and system criticality. Documentation of all inspections, test results and corrective actions must be maintained.

Who Is Qualified to Work on Solar PV and BESS Equipment?

Worker competence must be clearly defined, verified and maintained before assignment to electrical tasks. Competence levels include:

• General site workers: Not permitted to perform electrical work
• Instructed workers: Basic hazard awareness; supervised work only
• Authorised electrical workers: Trained, approved and assigned for specific tasks
• Qualified or competent persons: Fully trained, certified and authorized to make independent decisions

Appropriate Personal Protective Equipment

• Voltage-rated gloves (appropriate for DC and task voltage)
• Arc-rated clothing and jackets
• Eye and face protection
• Electrical safety footwear
• Insulated tools
• Suitable hard hat protection
• OSHA requires electrical protective equipment to be appropriate for the hazard and maintained in a safe, reliable condition.

How Should Workplaces Prepare for Solar or Battery Emergencies?

Effective emergency response requires advance planning, clear procedures and trained personnel.

Electric Shock Response

• Do not touch the casualty until the electrical source is controlled
• Activate emergency arrangements and call for help
• Arrange trained first aid responders
• Arrange urgent medical support and hospital notification

Arc Flash Response

• Raise the alarm immediately
• Isolate the affected area to prevent secondary exposure
• Obtain urgent medical evaluation for exposed workers
• Document the incident for investigation

Solar PV Fire Response

• Inform emergency responders that PV conductors may remain energised
• Provide shutdown diagrams and complete system information
• Restrict access until the hazard is eliminated
• Do not permit water suppression without specialist guidance

OSHA's guidance on solar energy LOTO specifically highlights that PV panels continue to generate energy and must be covered or isolated before workers begin maintenance — a principle that extends directly into emergency scenarios. See OSHA's solar lockout/tagout guidance.

BESS Fire or Thermal Runaway Response

• Activate the emergency action plan
• Evacuate personnel according to the site evacuation plan
• Notify specialist emergency responders with system details
• Consider smoke, flammable gas, explosion and re-ignition risks
• Do not permit uncontrolled re-entry to the area

NFPA advises that stationary energy-storage installations should be evaluated against the applicable requirements of NFPA 855.

Which Standards Apply to Solar PV and Battery Safety?

Multiple regulatory frameworks apply depending on installation jurisdiction:

• OSHA: Workplace electrical safety, PPE requirements, LOTO procedures and solar-worker protection standards (United States)
• NFPA 855: Standard for stationary energy-storage installation safety and fire protection
• UL 9540 and UL 9540A: Energy storage system product safety standards and thermal-runaway fire propagation testing methods
• NEC Articles 690 and 706: US National Electrical Code requirements for solar PV and energy-storage systems
• IEC 62548: International PV-array design requirements for DC wiring, electrical protection, switching and earthing
• IEC 62446: International PV inspection, testing, documentation and maintenance standards
• Local rules: National electrical codes, building codes, fire safety regulations and occupational-safety requirements

The applicable edition and legal status of each standard must be confirmed for the installation's specific jurisdiction.

Quick Solar PV and Battery Safety Checklist

Use this practical checklist to verify essential safety controls:

• Current single-line diagram available and accessible
• All AC, DC and battery energy sources identified
• Isolation points clearly labelled and accessible
• LOTO procedure approved and documented
• All cables and connectors undamaged and properly rated
• Grounding and protection devices verified and tested
• BMS and alarm systems operational and monitored
• Emergency shutdown system accessible and functional
• Workers appropriately trained and competent
• Emergency responders provided with system information

Build Stronger Solar and Battery Electrical-Safety Competence

Effective protection requires integration of multiple controls:

• Solar PV systems can produce persistent DC voltage even during darkness
• Batteries retain both stored electrical and chemical energy
• Effective protection requires comprehensive risk assessment, engineering controls, LOTO procedures, routine inspection, worker competence and emergency planning

Strengthen your ability to recognise hazards, evaluate electrical risks and apply appropriate workplace controls by enrolling in formal Electrical Safety training.

Always follow applicable legislation, approved site procedures, manufacturer instructions and advice from qualified electrical and fire-safety professionals.