Lockout/Tagout for Solar Installations

Technician applying lockout/tagout devices to solar PV electrical disconnects before maintenance.

Lockout/Tagout (LOTO) for Solar Installations: Safely Controlling Hazardous Energy in Photovoltaic Systems

Lockout/Tagout (LOTO) is one of the most effective methods for preventing electrical injuries during maintenance and repair work. While traditional electrical systems can often be fully de-energized, solar photovoltaic (PV) systems present unique challenges because solar panels continue generating electricity whenever exposed to sunlight.

This means that even after disconnecting utility power, portions of a solar installation may remain energized. Without proper lockout/tagout procedures, workers face increased risks of electric shock, arc flash, unexpected equipment energization, and serious injury.

Whether you're a solar installer, licensed electrician, maintenance technician, facility manager, or emergency responder, understanding how LOTO applies to solar energy systems is essential for safe work practices.

For a foundational understanding of how photovoltaic systems generate electricity, see Understanding How Solar PV Systems Work.

What Is Lockout/Tagout?

Lockout/Tagout (LOTO) is a safety procedure used to isolate hazardous energy sources before maintenance or servicing begins.

A proper LOTO program ensures that:

  • Equipment cannot be accidentally energized.
  • Stored electrical energy is controlled.
  • Workers can safely perform maintenance.
  • Only authorized personnel restore power.

LOTO requirements are established under OSHA 29 CFR 1910.147, commonly known as the Control of Hazardous Energy Standard.

Why Solar Installations Are Different

Unlike conventional electrical systems, solar panels produce electricity whenever sunlight strikes the photovoltaic cells.

Even after:

  • Opening the main service disconnect
  • Turning off the inverter
  • Disconnecting utility power

…the conductors between the solar array and the inverter may still carry dangerous DC voltage.

This is why solar installations require specialized lockout procedures that account for both AC and DC electrical systems.

For more information about continuously energized PV circuits, see Why Solar Panels Remain Energized.

Understanding Hazardous Energy Sources

A typical solar installation may contain multiple hazardous energy sources, including:

Solar Array (DC)

  • PV modules
  • String wiring
  • Combiner boxes
  • DC disconnects

AC System

  • Inverter output
  • AC disconnect
  • Service equipment
  • Distribution panels

Battery Energy Storage Systems (BESS)

  • Battery banks
  • Energy storage inverters
  • Battery disconnects
  • High-capacity DC circuits

Battery systems may remain energized even when the solar array has been isolated.

For more information, see [Battery Energy Storage System (BESS) Electrical Safety].

Solar LOTO Is More Than Turning Off a Switch

One of the most dangerous misconceptions is assuming that switching off an inverter completely de-energizes the system.

In reality:

  • PV modules continue producing DC voltage.
  • Capacitors inside inverters may retain stored energy.
  • Batteries may continue supplying power.
  • Multiple disconnects may need to be isolated.

Workers should never assume equipment is safe simply because it appears to be powered off.

Typical Lockout/Tagout Procedure for Solar Installations

Every installation should have site-specific procedures, but a typical sequence includes:

1. Identify All Energy Sources

Review:

  • Electrical one-line diagrams
  • Equipment labels
  • Inverter documentation
  • Battery system documentation

Determine every possible source of electrical energy.

2. Notify Affected Personnel

Inform anyone who may be affected that maintenance is beginning.

This helps prevent unauthorized operation of equipment.

3. Shut Down Equipment

Follow the manufacturer's recommended shutdown procedure.

This often includes:

  • Turning off the inverter
  • Opening AC disconnects
  • Opening DC disconnects
  • Disabling battery systems where applicable

4. Apply Lockout Devices

Install approved lockout devices on every applicable disconnect.

Each authorized worker should apply their own lock whenever possible.

5. Apply Warning Tags

Tags should clearly identify:

  • Person performing work
  • Date
  • Reason for lockout
  • Contact information

Never remove another worker's lock without following established procedures.

6. Verify Isolation

Never rely solely on disconnect positions.

Always:

  • Test for absence of voltage.
  • Verify your test instrument on a known live source before and after testing.
  • Check both AC and DC conductors.
  • Confirm stored energy has dissipated.

Testing is the only reliable method for confirming de-energization.

For additional guidance, see Understanding DC Voltage in Solar Systems.

7. Perform Maintenance

Only after hazardous energy has been controlled should maintenance begin.

Continue to remain aware that portions of the PV array may still be energized under sunlight.

8. Restore Equipment Safely

Before re-energizing:

  • Inspect tools and equipment.
  • Verify all personnel are clear.
  • Remove locks according to company policy.
  • Restore power using the proper startup sequence.

Rapid Shutdown Is Not Lockout/Tagout

Many newer PV systems include Rapid Shutdown devices required under NEC Article 690.

Rapid Shutdown reduces voltage outside the array boundary to improve firefighter safety.

However:

Rapid Shutdown does not replace Lockout/Tagout procedures.

Workers must still:

  • Follow OSHA LOTO requirements.
  • Verify absence of voltage.
  • Control every hazardous energy source.

Learn more in NEC Article 690: Solar Photovoltaic (PV) Systems Explained.

Common LOTO Mistakes in Solar Installations

Accidents frequently occur because workers:

  • Assume opening one disconnect de-energizes the system.
  • Skip voltage verification.
  • Ignore battery storage systems.
  • Remove another worker's lock.
  • Use damaged lockout devices.
  • Fail to identify all energy sources.
  • Trust equipment indicators instead of testing.

Every one of these mistakes can lead to serious injury or death.

Personal Protective Equipment During LOTO

Even during lockout procedures, workers may still be exposed to energized conductors while verifying isolation.

Appropriate PPE may include:

  • Voltage-rated rubber insulating gloves
  • Leather protector gloves
  • Arc-rated clothing
  • Arc-rated face shield
  • Safety glasses
  • Hard hat
  • Electrical safety footwear

PPE requirements should always be based on a hazard assessment.

For additional guidance, see Understanding Electrical PPE Requirements.

The Importance of Insulated Tools

Lockout/Tagout procedures frequently require technicians to remove covers, verify voltage, tighten terminals, or inspect energized equipment before establishing an electrically safe work condition.

Using IEC 60900 certified 1,000V insulated hand tools helps reduce the risk of accidental contact with energized conductors and minimizes the likelihood of short circuits while performing these tasks.

Insulated tools should always be used alongside proper PPE, voltage testing, and established LOTO procedures—they are an important layer of protection, not a substitute for safe work practices.

Learn more in IEC 60900: The International Standard for Insulated Hand Tools.

OSHA and NFPA 70E Requirements

Solar workers should understand the relationship between OSHA regulations and NFPA 70E.

  • OSHA establishes the legal requirements for controlling hazardous energy.
  • NFPA 70E provides best practices for achieving an electrically safe work condition, including risk assessments, PPE selection, and safe work procedures.

Together, these standards help create a comprehensive electrical safety program for solar installations.

For additional information, see:

Best Practices for Solar Lockout/Tagout

Every solar technician should:

  • Treat every PV system as energized until proven otherwise.
  • Identify every source of hazardous energy.
  • Lock and tag every applicable disconnect.
  • Verify the absence of voltage before beginning work.
  • Use properly rated insulated tools.
  • Wear appropriate PPE.
  • Follow manufacturer shutdown procedures.
  • Understand battery storage hazards.
  • Never bypass lockout devices.
  • Stay current with OSHA, NFPA 70E, and NEC Article 690 requirements.

Final Thoughts

Lockout/Tagout is one of the most important safety procedures for anyone working on solar photovoltaic systems. Because PV modules continue generating electricity whenever exposed to sunlight, solar installations require a more comprehensive approach to hazardous energy control than many traditional electrical systems.

By identifying every energy source, following OSHA-compliant LOTO procedures, verifying the absence of voltage, wearing appropriate PPE, and using IEC 60900 insulated tools, technicians can significantly reduce the risks of electric shock, arc flash, and unexpected equipment energization while maintaining or repairing solar installations.


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