125 Amp Service Installation Guide With Cost, Wire Size

125 amp service wire size, installation cost & complete guides

You have probably heard your electrician refer to the amps of your electrical service. But what do those terms mean? If your panel shows that you have 125-amp service, is that good or bad? Should you upgrade the amp service or leave it alone? This guide will give you an idea of what your amp service means and what you should do about it.

What Does 125 Amp Service Mean?

If you see 125 amps in the panel, your electrical service has a capacity of 125 amps. 125A is the total volume of electricity the bus bars can safely carry.

Your home’s electrical service size reveals the total capacity available to you. It shows you the volume of electricity that can flow through your home. The amperage of the electrical service is not random.

It can affect the number and size of the equipment you can run in your home.

The Spruce gave a basic explanation of the workings of a home’s electrical service.

Simply put, power reaches your home via the service panel. Most homes have two 120V service wires that will either pass overhead or underground. Regardless of where they pass, these wires will eventually stop at the service panel.

The panel distributes the electricity from the wires to the other branch circuits. The panel has a pair of bus bars that provide 120V each. You can determine the voltage of each branch circuit by looking at the number of bus bars to which it is connected.

If the branch circuit connects to one bus bar, you will get 120 volts of power. But if two bus bars connect to a branch circuit, it can access 240 volts. If you check the panel, it will tell you the total capacity of the electrical service.

Why Do I Need 125-Amp Service?

You have to select the electrical service carefully. The size matters because it affects the devices you can run on that electrical service.

Electrical services were so much smaller in the past. For instance, you had houses in the first half of the 20th Century with 30-amp panels. By the 1960s, many places had jumped to 60-amp panels. But 30 and 60A services are far too small to serve the needs of a modern home.

If you live in a contemporary house of 1,200 feet or more, 100-amp panels are the starting point. This is the minimum amp capacity the NEC expects to see. It gives consumers enough electricity to run all the essential items. That includes 240V appliances.

To be clear, 100 amps are still too low. You are more likely to find this capacity in older and smaller, the kind that don’t rely on high-end heavy-duty kitchen and laundry appliances, not to mention powerful air conditioners.

100A services are medium-capacity. If you have the option, you should upgrade to 125, 150, or even 200 amps. A 150A panel counts as a large capacity electrical service.

You can run all the heating and cooling systems you want without overloading your electrical service. 125-200A services are the norm. You are free to raise the capacity to 400 amps.

But the average house doesn’t require that much power. You only find 400A services in homes with items like hot tubs that consume immense volumes of electricity. If you ask your local contractor to upgrade the panel to a 400A service, they may ask you to evaluate your electrical demands to determine whether or not the amp service is necessary.

If you use ordinary household appliances and devices, they will probably tell you that 200A panels are adequate.

What Is Required For A 125-Amp Service?

125A services have the same requirements as those of any other service. The only significant concern is the breaker and wire size:

1). 100A Breaker Size

100A breaker can work on a 125A panel. The breaker matters because it protects the wires. Most people understand the importance of selecting the correct wire size.

The conductors should be large enough to transmit the current without overheating. Small wires will melt and start a fire. However, a wire cannot control the volume of electricity it carries.

In fact, you can force as much electricity through a conductor as you want. The only safeguard is the breaker. It will only permit a specific volume of electricity to pass through the wires.

The breaker will trip if you exceed that threshold, cutting the power off and saving the wires.

A small breaker is a nuisance because it will trip before your appliances acquire the power they need to operate. However, the solution is not a larger breaker because it won’t respond quickly enough to protect the wires.

Therefore, selecting the right breaker size is crucial. It can’t be too small or too large.

In the case of 125A panels, 100A breakers are perfectly fine.

Also, you don’t have to supply 125 amps to a 125A panel. You can use fewer amps. The difference between a 100A breaker and a 125A panel is too small to affect the operations of your appliance.

2). 1AWG Wire

You need 1AWG wire to accommodate a 100A service. But what about 125A? Do you have to increase the wire size? Not really. You can run a 125A service on 1AWG copper wiring.

You can use a slightly smaller wire depending on the temperature rating, distance, and material. You can’t ignore the fact that 1AWG and 2/0AWG wires are incredibly thick. Yes, they transmit a lot of electricity. However, their size makes them very stiff.

This is why it will be difficult to use with PVC conduit. However, you can still pull these cables through a pipe. But it requires a lot of time or effort. Your best bet is to use individual wires. Cables have jackets whose stiffness is bound to complicate the installation process.

How Can I Get A 125-Amp Service?

This question confuses laypeople because they don’t know what an electrical service means tangibly and practically. What gives your house 125 amps of power? What object must you replace to change from 100A to 125A?

Are you supposed to replace the entire electrical panel? No, you don’t have to replace the panel. Your only concern is the circuit breaker. Replace your pre-existing circuit breaker with a 125-amp circuit breaker.

Of course, it isn’t enough to change the breaker. You have to replace the service entrance cable and meter pan. Unless you have electrical experience, you should leave this task in the hands of a qualified contractor.

This isn’t a simple matter of pulling an old breaker out and snapping a new one in. You need an electrician to select and wire the new breaker.

How Do I Know If I Have 125-Amp Service?

You cannot determine whether or not your electrical service is suitable for your home if you don’t even know the amp rating of your electrical service. Some contractors expect consumers to identify the amps by looking at the meter’s design.

Apparently, the meter on a 100-amp service is a glass dome on a square base, while larger electrical service sizes use a rectangular base. On the other hand, you will find meters behind flat glass windows on 60-amp services.

This method of identifying the amp rating is confusing. It won’t make sense to the average homeowner. Some of them don’t even know what their electrical meter looks like or where to find it.

You are better off checking the main service panel. Ignore the smaller branch circuits. Their breakers have smaller ratings of 15 or 20 amps. Look at the main circuit breaker at the top.

The manufacturer will label it with an amp rating. The main breaker’s amp rating reveals the size of the electrical service. After all, the main breaker determines the power the house can access.

The 120V service wires connect to the main breaker, which is why laypeople should stay away from it. Let a contractor replace it. They can upgrade your electrical service size without getting shocked.

People whose homes use subpanels tend to assume that their electrical service size is the total of the main breaker’s amp rating and the subpanel’s amp rating.

But that is not accurate. The main breaker’s amperage is all that matters. The subpanel gets power from the main breaker. It doesn’t have access to the two 120V wires that bring power into your home.

The last thing you want is to assume that your home has a 225-amp service simply because the main breaker has 125 amps while the subpanel has 100 amps. If you have questions about your panels and subpanels, call your electrician for clarification. Don’t tamper with the panels and subpanels without supervision.

How Much Does A 125-Amp Service Cost?

It cost you $1,100. Though, in some cases, an estimate was as high as $2,700. The price will vary depending on various factors. For instance, the labor costs in some states are higher than in others. The retailer you use to acquire parts is just as important. Some stores are more expensive than others.

Your contractor will consider the task’s difficulty before providing a quotation: the more difficult the installation, the more expensive the job.

125 Amp Installation Cost

The average cost for installing 125-amp

TimeElectrician Cost/HourAverage Cost
Max Time 20 hrsMax cost $100$2000
Min Time 8 hrsMin cost $40$320
Average Time 14 hrsAverage cost $70$980

The labor costs can rise as high as $800 depending on the hourly rate and the job’s difficulty. Difficult jobs will take more time which, in turn, raises the overall cost.

Cost To Upgrade To 125-Amp Service

Upgrade to125 amp
Panel Cost$250
Average hour14 hr
Electrician cost$70
Average upgrade cost$1230

You can expect to spend $1230 or less, depending on the location, hourly rate, and difficulty of the job. Some upgrades will cost you as little as $500.

How To Install 125A Service?

  • Disconnect the power to the main leads at the meter
  • Screw knock-out clamps at the top or bottom. The location will depend on the way the service wires enter.
  • Run the main leads through the clamps. Secure them with a screwdriver.
  • Find the brass buss bars and run the black and red leads to the main lugs.
  • Find the silver bus and run the white lead to the main lug.
  • Pull a 10AWG ground wire into the panel. One end goes to the ground bus. The other goes to the ground rod.
  • Pull all the circuit wires you need through the clamps.
  • Remove the sheathing (8 – 12 inches) from the ends of the circuit wires.
  • Remove ½-inch of insulation from the ends of the individual wires.
  • Connect the white wire to the neutral bus and the bare wire to the ground bus.
  • Connect the black wire to the terminal of the circuit breaker
  • Push the circuit breaker into the hot brass bus bar slot
  • Run the red and black wires (220V circuit) to the two-gang breaker.

Who Should Install It?

You can install the electrical service yourself if you have the skill. But some states do not permit laypeople to perform electrical tasks like this one unless they have a license.

You are better off hiring an electrician or calling your service provider. They will send an electrician.

What Size Wire Is Required For 125 Amp Service?

You need 1-gauge copper wire for a 125A electrical service. If you prefer aluminum, aim for 2/0AWG.

125-Amp Service Ground, Hot, and Neutral Wire Sizes

  • Hot: 2– 1/0AWG
  • Neutral: 2 – 1/0AWG
  • Ground: 3/0 – 1/0AWG

How Many Wires Do I Need For A 125-Amp Service?

You will need three main service wires. A neutral wire and two black wires.

You will either pull them down or up to the breaker panel. This doesn’t include the cables for the various branch circuits.

Distance VS 125-Amp Service

The distance the wires have to travel affects the gauge. If the cables are too long, the voltage drop will increase. You have to raise the gauge to reduce the voltage drop. An electrician can help you calculate the voltage drop.

NEC Code

The NEC expects consumers to pair 125A loads with 1-gauge wiring.

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