Common Causes and Indicators of Electric Wiring Fires

Fire departments respond to an average of nearly 47,000 residential fires that involve some kind of electrical failure or malfunction each year, according to the National Fire Protection Association (NFPA). Of those instances, almost half are due to wiring issues in the home.

These claims can be costly. Fire and lightning insurance claim settlements average more than $75,000. Knowing the causes and common indicators of faulty wiring can help insurance professionals and policyholders alike understand why these fires occur. Adjusters can also use this knowledge to ensure that all evidence is considered when determining how to settle a fire-related claim.

Electrical Fire New

The Insurance Information Institute reports fire as one of costliest causes of loss, despite accounting for only about a quarter of homeowners insurance losses.

A Hidden Threat

Most homeowners don’t think about wiring. Though it’s essential to the function and comfort of a modern house, it’s often hidden within the walls, behind furniture, or in attics. The adage “out of sight, out of mind” applies here, and this can have far-reaching consequences when maintenance and precautions are neglected. 

Origin and cause investigations often locate the area of origin in a hidden part of the home, such as inside a wall cavity, crawlspace, or attic. The fact that the initial sparks may go unnoticed is one reason electrical fires are likely to spread beyond the point of origin quickly. Wiring can be situated near several items that can ignite, including insulation and carpeting, making it possible for the resistance heating from a loose connection to become a raging fire within seconds to minutes.


Electrical arcing is a common phenomenon in exposed and frayed wiring in which electricity jumps from one connection to another. As described above, arcs from wiring can ignite the combustible materials that surround it and quickly spread past the point of origin. 


Arcing in faulty wiring and loose connections generates high-temperature sparks that can ignite surrounding materials, leading to destructive fires.

Homeowners can contribute to the threat of arcing through routine activities without even realizing it. For example, wires can be pinched by doors, windows, or moving furniture, wearing down protective insulation. Nails and screws in the wall may puncture the wire insulation during home repairs or redecorating. Even walking on a carpet laid over wiring can generate enough heat to weaken it.

Outdated Wiring

The number of electronics used in homes has increased exponentially in the last few decades, contributing to the complexity of electrical fire claims. Older homes could lack the capacity to handle growing electricity usage; wiring in a home more than 20 years old may not be designed to power multiple desktop and laptop computers, televisions, video game systems, and various appliances. 

In addition, many older homes are outfitted with aluminum wiring and connectors rather than copper. Aluminum is more prone to deteriorate, leading to a much higher risk of fire. In fact, the Consumer Product Safety Commission found that older homes with aluminum wiring are up to 55 times more likely to experience fire hazard conditions than homes with copper wiring. Origin and cause experts investigating possible electrical fires seek to determine the material and age of the wiring in the house, as well as to confirm the equipment it was powering at the time of the fire.


These aluminum wires collected from a fire loss site exhibit signs of arcing and melting, common in this type of wiring.


Certified fire investigators follow NFPA guidelines during their inspections and take all possible causes of loss into account, stacking evidence and observations against their hypothesis. During interviews, policyholders and other witnesses may provide background information that could indicate a wire-related electrical fire, including reports of: 

  • Flickering lights/intermittent power outages
  • Appliances or electrical devices hot to the touch
  • Shocks or sparks from appliances or outlets
  • Unexplained burning smells

Experts can also identify an array of onsite indicators that point toward wiring as a potential cause of loss, including outdated wiring, worn or damaged insulation, scorch marks in or on electrical outlets, and rerouted cords. All evidence has to be weighed against other observations and scientific knowledge, but an experienced investigator has a trained eye to notice indicators that might otherwise be missed. 

Crimped Wiring

Rerouting is just one indicator to experts that stress has been placed on wiring, increasing its risk of deterioration that can lead to fire.

An expert in fire analysis knows what to look for even when evidence isn’t in plain sight. Donan’s certified fire investigators have years of experience, are committed to NFPA guidelines and the scientific method, and are supported by a network of licensed electrical engineers to provide answers to even the toughest origin and cause assignments. 

To get the benefit of a claim assessment partner who knows what to look for onsite and takes all evidence into account – in electrical fire claims and beyond – submit an assignment to the Donan Fire Investigation team.