Can Rats & Mice Damage Electrical Wiring?

Rodents chew wiring because they gnaw constantly, and a cable is just another thing in their path. Their incisors keep growing throughout life; peer-reviewed research describes rodents as mammals that “exhibit the ability to continuously grow their teeth,” with enamel shaped to self-sharpen as they gnaw.

Wire makes a convenient target. It runs along the same joists, top plates and wall cavities rodents use as highways, it is the right thickness to grip, and its plastic jacket is soft enough to bite through. Extension sources name both species:

• Mice: University of Nebraska-Lincoln Extension says they “will gnaw electrical wiring, soap, and other items of comparable hardness.” UC IPM adds that they “can chew on the cords of appliances as well as wires in walls.”
• Rats: UC IPM says rats “commonly gnaw on the insulative sheaths of engine wires in cars,” which matters if you park in a garage where rodents are active.

For everything else rodents do to a house, from insulation to stored belongings, see our guide to rodent damage in homes.

Rodent-damaged wiring shows the same signs as any wiring fault, so treat them seriously whatever the cause. The Electrical Safety Foundation International (ESFI) lists these warning signs of home wiring hazards:

• Circuit breakers that frequently trip, or fuses that often need replacing.
• Dim or flickering lights.
• Arcs and sparks: “flashes of light or shower of sparks anywhere in your electrical system.”
• Sizzles and buzzes from the electrical system.
• An odor of hot insulation, or switch plates and receptacle covers that are hot to the touch or discolored.
• Electrical shocks: “any shock, even a mild tingle, may be warning of an electrical danger.”
• “Damaged wire insulation - cut, broken or cracked insulation.”

What points to rodents is the combination. A breaker that starts tripping the same month you hear scratching in the ceiling, or a dead outlet near fresh droppings, is worth connecting. Look along the cable too: a gnawed jacket looks nicked or stripped, often with plastic shavings on the joist below.

Wiring damage happens where cables pass through the spaces rodents live in, which are mostly the spaces you rarely see. In a Chesapeake house, those are:

• The attic: cables stapled across ceiling joists and along top plates, and junction boxes for ceiling lights and fans.
• Inside walls: cable runs between floors, especially near plumbing, where mice often travel.
• The crawl space: wiring stapled to floor joists, a few inches above the soil where Norway rats burrow.
• The garage: ceiling wiring, the door opener, and the wiring of any car parked there.
• Behind appliances: cords for the refrigerator, washer, dryer and freezer, where crumbs and warmth draw mice.
• Where service lines enter the house: a gap around a service line is both a doorway and a chewing spot.

Chewed wiring is an electrical safety risk because the insulation is what keeps live conductors from touching each other, the framing or you. Once it is gnawed away, ESFI’s hazards apply directly: arcs and sparks, overheating and shocks. UC IPM lists electrical sparks and fires among the safety concerns that come from rat gnawing.

You do not need a number to act. We give no figure for how many house fires rodents cause, because we have found no authoritative source for one, and damaged wire insulation is on ESFI’s hazard list on its own.

House age adds a second reason to get wiring checked. ESFI recommends an electrical inspection when a home is 40 or more years old, or when you are a new owner of a previously owned home. In Chesapeake, 31.7% of homes were built before 1980 (U.S. Census Bureau, ACS 2020-2024), and in the ZIP code area that covers much of South Norfolk the figure is 59.3%. In an older house that has had rodents, one electrician’s visit answers both questions.

If you find chewed wires, keep your hands off them and call an electrician. ESFI’s advice for any of its warning signs is to have an electrician inspect the wiring.

Take these steps in order:

1. Do not touch exposed wire. If the cable is live, contact with bare copper can shock you.
2. Cut power at the breaker if it is safe to do so and you can identify the circuit, especially if you see sparks, smell hot plastic or find a warm switch plate.
3. Unplug and replace damaged appliances. The U.S. Fire Administration says “If the appliance has a cracked, damaged or loose cord, replace the appliance.”
4. Call an electrician to inspect and repair the wiring.
5. Photograph the damage and any nearby droppings before anything is cleaned up, for the electrician and any later conversation with your insurer.
6. Call rodent control so the cause is dealt with before or alongside the repair.

Active sparks or smoke are an emergency: call 911.

Remove the rodents before the wiring is repaired, or the new cable becomes the next thing to chew. A repair fixes the damage; it does nothing about the animals still using the same runs.

The electrician makes the circuit safe now; full repairs work best once removal and sealing are underway. Tell us where the electrician found damage, and we know which runs, rooms and entry points to focus on.

Chesapeake Rodent Control handles the rodent side, inspecting inside and out before we remove whatever is living in those runs:

• For mice, humane trap and bait placement through our mouse control service.
• For roof rats or Norway rats, exterior bait stations, burrow and nesting-site treatment and trapping through rat control in Chesapeake.

We do not repair electrical wiring. That stays with your electrician.

Preventing repeat damage means keeping rodents out of the spaces where wires run. UC IPM’s rule is that “All holes larger than 1/4 inch should be sealed to exclude both rats and mice,” and that includes the gaps around every utility line entering the house.

What makes the biggest difference:

• Close the gaps around service entries for good, using hard materials rather than a squirt of foam. Our rodent proofing service handles the full exterior seal, door sweeps and vent screening.
• Trim the ladder. UC IPM advises pruning tree limbs “within 3 feet of a roof” so climbing rats cannot reach the roofline.
• Clear clutter from the garage and attic, so wiring runs stay visible and nesting spots are fewer.
• Store pet food, birdseed and grass seed in sealed containers.
• Keep the follow-up visit, when traps and bait stations are rechecked and treatment is adjusted if activity remains.

Proofing visits run $180 to $250 on our published price list, and the technician confirms your price on the callback. Call (757) 551-3952, 7am to 8pm any day, or request a free callback.