Electrical wiring is an essential part of any home. I often describe it to people as the house’s circulation system.
Buying a newer home will be up to the current building and electrical codes and should not possess serious hazards. However, older homes built pre-1970 may raise some concerns about the electrical wiring. If you’re living in or buying an old house, the wiring will eventually need to be updated.
Electrical wiring has a life expectancy of 50 to 70 years. The copper in electrical wiring can last over 100 years; however, the outer protective sheathing will degrade much sooner. Plastic-sheathed wiring lasts longer than fabric-sheathed wiring commonly found in pre-1970 houses. Wiring older than 1970 likely is near the end of its useful life.
However, age is not the only determining factor. There are a lot of details when it comes to the lifespan of electrical wiring.
You should replace electrical wiring if it is ungrounded or has damaged protective sheathing. Ungrounded wiring lacks a bare copper ground wire grounding the circuit to the electrical panel. Electrical wiring with damaged sheathing may be repairable; however, severe damage could require a partial or complete wiring replacement.
In this article, I would like to show you what type of wiring you may find in a home, including warning signs it’s time to replace all or part of your home’s electrical wiring.
How Long Does Electrical Wiring Last?
The average life expectancy of electrical wiring is about 50 to 70 years. Electrical wiring life can be shorter, depending on how the wiring is installed, damage to the sheathing, and past modifications.
Romex electrical wire sheathing can last 80 years or longer. The plastic sheathing doesn’t degrade as fast as cloth-sheathed wiring. The biggest threats to plastic sheathing are heat and animals like squirrels and mice.
On their own, electrical wiring materials can last a long time. For example:
- Copper wires can last over 100 years.
- Aluminum wires can last between 80 and 100 years.
However, it is not that simple, and often electrical wires are not installed in perfect condition. There’s much more that needs to be considered.
- The contractor may not install electrical wiring correctly.
- Environmental factors in the electrical wiring installed are often not ideal.
- The electrical wiring may be faulty due to unpermitted remodeling, improper handyman, or DIY work.
- Advances in electrical codes throughout the years.
All this will affect the protective sheathing, often referred to as insulation. The protective sheathing will degrade and wear out more quickly than the wire. The central aspect determining electrical wiring life expectancy is the protective sheathing condition.
With time, the insulation will become dry and brittle. Eventually, it degrades, exposing the wiring and creating shock or fire hazards, a significant safety issue.
What Materials Are Used in Electrical Wiring?
Electrical wires can be made from different materials. Knowing a little more about each of the most commonly used materials is good. They all have distinct advantages and disadvantages.
1. Copper Wiring
Copper is the most widely used material for wire manufacturing today. A few qualities that are specific to copper make it the go-to metal.
- It is an excellent conductor and transfers electricity with ease.
- Copper wires are easy to bend and place in different spots in the house.
- Copper is also a reasonably easy metal to mine and extract. It is not as abundant as some other metals, but the relative ease of finding it makes it a good option.
2. Aluminum Wiring
Aluminum is more abundant in nature than copper, making it cheaper than other metals.
One of the downsides of aluminum is that it is not as good a conductor as copper. Technically, you will need wires with a bigger diameter to carry the same electricity as copper wires.
For example, to have the same conductivity as copper wire with a cross-section of 100 mm, the aluminum wire will have to be about 156 mm.
Aluminum wiring can be dangerous in older homes built during the 1960s and 1970s.
An investigation carried out by the U.S. Consumer Product Safety Commission (CPSC) concluded that older homes built before 1972 (that had aluminum wiring) are 55 times more prone to electrical fires. The investigation looked only into the wire connections at the outlets. So these rates may even be higher.
There were no official investigations and statements about homes built with aluminum wiring after 1972. Many homes built in that period had aluminum wiring because the U.S. was going through a severe copper shortage at the time.
Many manufacturers switched to more abundant aluminum for their wiring and, in some cases, even produced electrical panels and breakers (which is the case with Zinsco electrical panels).
The main thing that makes aluminum wiring dangerous is not necessarily the wiring itself. But instead, the connection points (The places where the wire connects to any switches, receptacles, junction boxes, panels, and more).
- The problem with aluminum wiring is that it generates heat when electricity passes through the wires. The heat will cause aluminum to expand when hot and contracts as it cools. Eventually, this causes the wiring connections to become loose. A loose connection like this can cause arcing, which can start an electrical fire.
- Another problem comes from the diameter of the wires. The wires installed during that period were of a smaller diameter. Aluminum wires cannot carry the electrical current that a copper wire of the same size can. Nowadays, the increased electrical demands can lead to overheating the wires creating a severe electrical fire hazard.
Some stranded aluminum wiring is still used in houses today for the main service entry wires and other 240-volt circuits like ranges and clothes dryers. Stranded aluminum wire is much safer than solid aluminum wire.
Federal Pacific Stab-Lok breaker panels also had solid aluminum branch wiring. If you have a Federal Pacific panel in your home, our article Are Federal Pacific Breaker Panels Safe? Dangers & Cost to Replace we discuss some of the main problems concerning these panels.
3. Alloys and Silver Wiring
Different aluminum, copper, and silver alloys are also used for electrical wire production. They are usually used in the industrial sector and are not found in residential buildings.
Silver is considered to be the best conductor. However, its high cost often makes it unsuitable, especially when copper and aluminum are way cheaper and more readily available.
The Different Types of Wiring
In addition to the materials used to manufacture the electrical wires, we may face some inherent problems with the different types of wiring.
There have been many different wiring practices throughout the years. Electric wires came with varying types of insulation. Knowing and recognizing these may help any new homeowner identify potential hazards and points of concern.
1. Knob and Tube Wiring
According to industry professionals, while grandfathered into the electrical code, knob, and tube (K&T) wiring is considered dangerous and unsafe. Unless rewired, you can find K&T wiring in homes built between the 1880s and the 1940s.
The ceramic tubes are durable and can last many years if not damaged. However, the wiring and its insulation, particularly, are subject to natural wear and tear. Also, rodents and other animals may try to chew through the wires.
The main disadvantages of the K&T wiring are:
- Insulation becomes brittle with time. Contractors considered K&T wiring top of the line in its day. However, there is no way of getting around it; this type of wiring is obsolete. Even if the wiring appears to be working fine now, there is no guarantee for how long it will be able to continue.
- The wiring needs to breathe, so adding insulation is not recommended (it has been strictly forbidden by the National Electric Code (NEC) since 2008). Electricians state that if K&T wiring is damaged or disturbed, you should replace the entire wiring system.
- K&B wiring lacks grounding, leading to higher risks of electrical shocks.
It usually is not permitted to extend or modify knob and tube wiring in any way. These restrictions can leave homeowners with electrical wiring unsuitable for today’s higher electrical needs and no means to address the condition without extensive renovation.
Electronic devices build up static electricity. Without proper grounding, this makes the circuit is susceptible to lightning strikes. For this very reason, many older homes have lightning rods on the roof of the house grounded by aluminum wiring to a grounding rod.
2. Cloth Sheathed Wiring
Cloth wiring is another tricky topic for most home inspectors, electricians, and insurance companies. Cloth-sheathed wiring is frequently found in home properties contractors built before 1970.
One of the main problems with cloth wiring is its age. Although considered by a lot of people safe, the insulation will become brittle with time. When the sheathing fails, it becomes frayed. As both the rubber and cloth are wearing down, this is unsafe and can lead to arcing and shocking hazards.
Some common problems that you can find with cloth-sheathed wiring:
- They pose a fire hazard due to the insulation becoming brittle and possibly falling apart.
- Below the cloth sheathing was a layer of paper insulation.
- Cloth-sheathed wiring doesn’t have a grounding wire.
- Wires may become hot and expose surrounding areas to heat.
- Cloth wiring is known to contain asbestos, which is a known carcinogen.
3. Plastic Sheathed Wiring
Polyvinyl Chloride (PVC) is one of the most widely used materials for cable production. However, it is becoming less popular due to health, safety, and environmental concerns.
One of the dangers of PVC wiring is that many wires are confined in a small area, leading the wires to overheat.
- The PVC sheath can burn in that case.
- Another thing is that when burning, PVC releases toxic fumes.
- PVC is not suitable for recycling.
- Some PVC wiring lacks a grounding wire.
4. Non-Metallic (Romex) Wiring
Non-metallic (NM) wires are one of the most widely used types of wires. They can last a long time because of the heavy insulation they have. An NM wire consists of a hot, neutral, and ground wire, each individually insulated. And then, all the wires are insulated with one more layer of PVC plastic.
How long does Romex wiring last? Non-metallic (Romex) wiring can last 70 years or longer. The outer protective sheathing resists breakdown due to age. Commonly, damage to Romex wiring is caused by animals or overheating, which requires a partial wiring replacement.
This makes them very durable, flexible, and easy to install.
5. Armored Wiring
Armor Clad (BX) wiring is very similar to the N.M. cables. The only difference is that the wires are insulated and covered by a flexible spiral made from aluminum or steel, which serves as a flexible conduit.
The BX wires are incredibly durable and can last a long time. BX wire is relatively easy to install. The only downside is that they are significantly more expensive than an NM cable. BX is commonly found in commercial applications.
Is Old Wiring Dangerous?
One of the main things that need to be checked is the age of the wiring. If an older house has never been rewired, this may mean that the wiring is original and likely needs to be updated.
In some cases, even wiring installed 25 years ago can be considered dangerous and need replacement. Most older electrical systems will not have arc fault circuit protection (AFCI) or ground fault circuit protection (GFCI). These safety measures have been added in recent years to protect homeowners and renters better.
Old wiring frequently comes with some risks.
- If the wires have compromised or frayed insulation or are exposed, there is a chance we can contact them. Frayed wire can lead to various electrical faults, shocks, and electrocution.
- Worn-out cables or loosely connected and faulty wiring can lead to arcing, which produces tremendous amounts of heat. Worn sheathing will expose the wire to high temperatures, which can cause an electrical fire.
- Previous inhabitants will likely modify older wiring in a DIY style. Today the wiring system in homes has to comply with many rules. Old wiring may be more likely that people have tried to modify it and adapt it to their needs over the years. The wiring may not be code compliant or even safe anymore.
- Older wiring was installed with lower amperage in mind compared to the requirements of today’s electrical appliances. Today’s electrical needs are often too much for ungrounded wiring, which overloads the circuitry.
What’s the Cost to Rewire a House?
Rewiring a house is a costly endeavor. How often you should rewire a home depends mainly on the age of the house and the type of wiring present.
The average cost to rewire a 2000 square foot can cost $12,000 to $20,000. Larger houses will cost more. You can expect to pay between $6 and $10 per square foot. Costs will vary based on house size, the number of circuits, and electrical panels relocation. The National average is approximately $8000.
It’s impossible to give an exact cost here as several factors affecting pricing exist. The actual charge will vary from property to property. Getting three quotes from licensed electricians before settling for a particular one is recommended. Avoid hiring an unlicensed contractor to rewire a house.
Factors affecting the cost of rewiring a house include:
- The contractor is upgrading the service entry wires, meter base, service mast, and weather head.
- The number of circuits will increase as in older houses; circuits often cover multiple rooms. Current electrical codes require circuits for each room and, in some cases, separate circuits between lights and outlets due to the current electrical code’s arc fault and ground fault protection requirements.
- The contractor is updating the current electrical panel box to 200 amp service.
- The electrical contractor’s specialty can be a cost factor. Commercial electrical contractors often don’t like taking residential rewiring jobs and often charge a premium.
- The electrical contractor’s schedule can often be a factor. Busy contractors often price rewiring jobs at the total price or even ballpark the price because they are already overloaded with work.
- The contractor is adding arc fault circuit interruption (AFCI) protection. AFCI protection is required in all rooms now under the National Electrical Code. AFCI breakers are more expensive than standard breakers due to their built-in electronic sensor.
- They are adding ground fault circuit interruption (GFCI) protection. GFCI protection is required in wet areas under the National Electrical Code. GFCI outlets and breakers cost more than standard ones due to their built-in electronic sensors.
Be wary of any electrical contractor who agrees to do any significant electrical work, such as rewiring a house, without pulling the proper permits. Also, be sure the electrical contractor you choose is licensed, insured, and bonded.
Suppose you are purchasing a home with old, outdated, or faulty wiring, and you have no other choice but to have it replaced. In that case, you can consider renegotiating the cost of the home, or you can ask for the repairs to be covered by the seller before you move in.
Electricians will examine any potential hazards and issues during a home inspection and determine if further investigation is needed.
You can do a DIY home inspection during the purchase process before making a formal offer, but this should not stand in place of a professional home inspection. See our Home Inspection Checklist.
How Long Does It Take to Rewire a House?
Rewiring a single room (for example, a kitchen) can take one to two (1 to 2) days. Rewiring an entire house can take one to three (1 to 3) weeks, depending on the scope of work that needs to be done.
Rewiring a house is not just cost-consuming but also time-consuming. Frequently this needs to be well-planned.
The time needed will vary depending on the following:
- The size and age of the home will affect how long the rewire will take.
- Overall conditions of the house. Houses in poor condition pose hazards that could slow down the workflow.
- The number of electrical circuits needed will determine how many circuits will be needed.
- The type of existing electrical panels and wiring could shorten the contractor’s rewiring time to salvage the existing service.
- Demolition work will significantly affect cost. The above costs do not include interior wall and ceiling repairs.
Replacing the wiring is inconvenient because your home will be without electricity during that time. You’ll likely need to move out while the house is being rewired.
Will Old Wiring Affect Home Insurance?
Older and outdated wiring may affect your insurance.
Some insurance companies may refuse to insure the house until the wiring is replaced. In these cases, insurance companies may agree to insure the home if it passes an electrical inspection. They may charge you a higher premium depending on the age of the electrical system.
Speaking directly with the insurance companies to determine their official statement is advisable.
Frequently they may care more about the types of circuit breakers and the electrical panel installed in the property instead of the wiring itself.
Do Older Homes Need Rewiring?
If you own a house built pre-1990, you may wonder if you should rewire your home.
Should you rewire a house built in the 1980s? You shouldn’t need to rewire your home unless you experience electrical issues such as dimming lights, tripping breakers, etc. However, you are approaching the age threshold, and we recommend having an annual electrical inspection performed by either a certified home inspector or a licensed electrician.
Should you rewire a house built in the 1970s? If your home were built in the 1970s and has all original electrical panels and wiring, you would benefit from an electrical upgrade. The house likely has an older panel box and ungrounded wiring. An annual home inspection by a certified home inspector or a licensed electrician should be a top priority.
Should you rewire a house built in the 1960s? If your home was built in the 1960s and has all original electrical panels and wiring, you likely need to upgrade the electrical wiring and panels. The house probably has an undersized electrical panel box, ungrounded cloth-sheathed wiring, outlets, and switches. We would recommend that you have an electrical inspection performed.
Should you rewire a house built in the 1950s or before? Suppose your home was built in the 1950s or before and has all original electrical panels and wiring. In that case, you are beyond the age threshold where rewiring your home is most likely needed for both modernization and safety concerns. We recommend thoroughly examining the entire electrical system performed by a licensed electrician.