Installing solar panels on rooftops can pose a serious fire hazard if the electrical equipment is improperly wired. Although fires caused by rooftop solar panels are rare, they can spread rapidly and destroy entire homes before emergency responders can intervene.

According to Solarstone, the majority of fire accidents in solar energy systems are a result of DC arcing. To mitigate this dangerous threat, homeowners can use an Arc Fault Circuit Interrupter (AFCI) that detects and shuts down circuits with electrical irregularities.

This blog discusses the prevention of solar rooftop fires with AFCIs. Discover more about AFCIs, their function, and how they safeguard against potential fires.


Arc Fault Circuit Interrupters (AFCIs), also known as Arc Fault Detection Devices (AFDDs), are specialized circuit breakers that are capable of identifying and shutting down circuits when electric arcs are detected.

The purpose of an AFCI is to distinguish between harmless arcs and dangerous arcs.

Harmless arcs occur during normal everyday actions, such as moving switches or plugs. By contrast, dangerous arcs have the potential to cause fires. An open wire in a lamp cord is an example of a dangerous arc.

How Arcs Form

An arc is formed by the ionization of air between two conductors or between a conductor and the ground, resulting in the breakdown of air voltage. Arcs can generate high temperatures and even open flames.

In electrical systems, these arcs damage insulation materials and prevent them from working properly. Arcs can also easily ignite nearby materials.

In solar energy systems, arcs may be caused by various factors such as loose terminals, poor contact, and broken cables. Arcs can also be caused by corrosive equipment, damaged insulation materials, or damp wires.

Considering these risks, incorporating AFCIs into rooftop solar installations is crucial.

How AFCIs Work

The primary function of an AFCI is to serve as a safety device and monitor the current flow through it. It is designed to detect abnormal situations like arcing, short circuits, and nonperiodic waveforms.

Once such conditions are detected, the AFCI trips its internal contacts. This effectively cuts off power flow, preventing the occurrence of any potential fires.

Detecting an arc involves identifying spikes at a specific frequency and an excessive number of discontinuities.When detecting an arc, it’s important to pay attention to frequency (the number of times per second) and amplitude (the height or depth of a peak).

Under normal conditions, an AFCI should not trip (i.e. shut off). AFCI electronics allow the system to function when there is a surge in current. Different types of sensors, including thermal, instantaneous, and load current sensors, have proven to be effective in various situations.


AFCIs offer advanced protection against electrical shorts and faulty wiring. They significantly reduce the risk of devastating fires in homes equipped with solar panels.

It’s crucial to implement comprehensive measures, such as intelligent arc detection and rapid shutdown technologies, to enhance the safety and control of solar energy systems.

Image Source: SolaX Power,