Electrical Sub-Panel Sizing Calculator

The size of an electrical subpanel depends on the total amperage of the circuits it will serve. Common residential subpanels are 100-amp or 200-amp, but they can vary. Consult with a qualified electrician to accurately determine the appropriate subpanel size based on your specific electrical needs and local codes.

Here’s a table summarizing common electrical sub-panel sizes and their corresponding amperage ratings:

Sub-Panel Size	Amperage Rating	Typical Use
60-Amp	60 amps	Smaller residential projects
100-Amp	100 amps	Most residential applications
125-Amp	125 amps	Larger homes or workshops
150-Amp	150 amps	Residential with extra circuits
200-Amp	200 amps	Large homes and some commercial

Keep in mind that sub-panel sizing should consider the total electrical load and local code requirements, so consult with an electrician for precise recommendations.

FAQs

How do I know what size sub panel I need?

The size of the subpanel you need depends on your specific electrical requirements. To determine the size, calculate the total amperage of the circuits you plan to connect to the subpanel. A common choice is a 100-amp subpanel for residential use, but it can vary. It’s best to consult with a qualified electrician for a more accurate assessment based on your needs.

Can I run a 100 amp sub panel off 200-amp main?

Yes, you can run a 100-amp subpanel off a 200-amp main panel. The subpanel’s amperage rating can be lower than that of the main panel, but it should not exceed the main panel’s capacity.

How many circuits can be on a 40 amp sub panel?

A 40-amp subpanel can typically support several circuits, but the exact number will depend on the load of each circuit. As a rough estimate, you could have around 8-10 circuits with 15-20-amp breakers in a 40-amp subpanel.

How many sub panels can you have on a 200-amp service?

You can have multiple subpanels on a 200-amp service, but the number will depend on the total load of all the subpanels and the main panel. A qualified electrician should assess your specific electrical needs to determine the number of subpanels that can be safely added.

What size wire do I need for a 200 amp service?

For a 200-amp service, you typically need copper wire sized at least 2/0 AWG (American Wire Gauge) or aluminum wire sized at least 4/0 AWG for the service entrance conductors. However, this can vary depending on local electrical codes and the length of the run, so consult a professional electrician for precise sizing.

How to tell the difference between 100 amp and 200 amp service?

You can often identify the difference between 100-amp and 200-amp service by looking at the size of the service entrance cable and the main breaker in the electrical panel. A 100-amp service typically has a smaller cable and a 100-amp main breaker, while a 200-amp service has a larger cable and a 200-amp main breaker.

Do I need a grounding rod for a sub panel?

Yes, a subpanel typically requires its own grounding rod. It should have a separate ground bar that is bonded to the panel’s enclosure, and this ground bar should be connected to a grounding electrode, such as a ground rod, driven into the earth. Local electrical codes may specify the requirements for grounding subpanels.

How many circuits can be on a 100 amp sub panel?

The number of circuits in a 100-amp subpanel depends on the load of each circuit. As a rough estimate, you could have around 20-30 circuits with 15-20-amp breakers in a 100-amp subpanel.

What gauge wire do I need for a 100 amp sub panel?

For a 100-amp subpanel, you typically need copper wire sized at least 3/0 AWG or aluminum wire sized at least 2/0 AWG for the feeder conductors. However, consult local electrical codes and an electrician for precise sizing based on your specific installation.

Can you overload a subpanel?

Yes, it is possible to overload a subpanel by connecting too many circuits or devices that draw more current than the subpanel’s amperage rating can handle. Overloading can lead to overheating, tripped breakers, or even electrical fires, so it’s important to size the subpanel appropriately for your needs.

Can I run 50 amps to a 100 amp sub panel?

Yes, you can run a 50-amp circuit to a 100-amp subpanel as long as the subpanel’s overall load does not exceed its 100-amp rating. The subpanel should be properly sized for the total load it will serve.

How many wires can be from the main panel to a sub panel?

The typical wiring configuration from a main panel to a subpanel includes four wires: two hot (phase) conductors, one neutral conductor, and one equipment grounding conductor. This setup allows for a safe and balanced electrical connection between the panels.

What is the 6 throw rule?

The “six-throw rule” is a guideline used to determine if a disconnect switch is required when installing multiple disconnecting means for a single service or feeder. If there are more than six disconnect switches (or throws) in total between the service entrance and the branch circuits, a single main disconnect switch may be necessary to meet electrical code requirements.

Can I run 2 100 amp sub panels off 200 amp service?

Yes, you can run two 100-amp subpanels off a 200-amp main service, provided that the total load from both subpanels does not exceed the capacity of the main service (200 amps). Each subpanel should have its own feeder circuit and appropriate overcurrent protection.

Can I run a 200 amp sub panel off 200 amp main?

Technically, you could run a 200-amp subpanel off a 200-amp main panel, but it’s important to consider the total electrical load and ensure that the main panel’s capacity is not exceeded. This would typically be done in large residential or commercial applications.

How far can you run 200 amp service underground?

The maximum allowable distance for running 200-amp service underground can vary depending on local electrical codes and the size and type of the conductors used. In general, it’s best to consult with a qualified electrician who can assess your specific situation and ensure compliance with local regulations.

What size wire do I need to run 40 amps 200 feet?

To run 40 amps over a distance of 200 feet, you would typically need copper wire sized at least 6 AWG or aluminum wire sized at least 4 AWG. However, this can vary depending on the voltage and specific installation requirements, so consult with an electrician for precise sizing.

How much does it cost to go from 100 amp to 200 amp service?

The cost of upgrading from a 100-amp to a 200-amp service can vary widely depending on factors like location, existing wiring, and labor costs. As a rough estimate, it could cost anywhere from $1,500 to $4,000 or more.

Is it worth upgrading to 200 amp service?

Upgrading to 200-amp service can be worth it if your electrical demands have increased or if you plan to add more circuits and appliances to your home. It provides more capacity for future growth and can improve the overall performance of your electrical system.

What is involved in upgrading from 100 amp to 200 amp service?

The process of upgrading from 100-amp to 200-amp service typically involves obtaining permits, replacing the main electrical panel, upgrading the service entrance conductors, installing a new meter socket, and ensuring that the grounding and bonding meet current code requirements. It’s a complex job that should be done by a licensed electrician.

How many 220 breakers can be in a 100 amp panel?

In a 100-amp panel, you can typically have multiple 220-volt (240-volt) breakers, but the exact number will depend on the specific panel’s design and the total load it’s rated to handle. As a rough estimate, you might have space for 4-6 double-pole 220-volt breakers in a 100-amp panel.

How far off the ground should a sub panel be?

The National Electrical Code (NEC) generally requires that a subpanel be installed at a height between 48 and 66 inches above the floor or working surface. However, local codes may vary, so it’s important to check with your local authorities for specific requirements.

What is the electrical code for grounding a sub panel?

The electrical code typically requires that a subpanel be properly grounded. This involves connecting a separate grounding conductor to a grounding bar in the subpanel and ensuring that it is bonded to the main panel’s grounding system. The specific code requirements may vary by jurisdiction, so it’s important to consult local codes and a qualified electrician.

Do you need to run a neutral wire to a sub panel?

Yes, you need to run a neutral wire to a subpanel. The neutral wire is necessary to provide a return path for unbalanced current in the circuits connected to the subpanel. It helps ensure that the electrical system operates safely and efficiently.

Can I run a 100 amp sub panel off a 150 amp main panel?

Yes, you can run a 100-amp subpanel off a 150-amp main panel, as long as the subpanel’s total load does not exceed its 100-amp rating. The subpanel should be properly sized for the intended circuits.

Does a 100 amp sub panel need a main breaker?

A 100-amp subpanel typically does not require a main breaker if it is fed directly from the main panel and does not have more than six breakers or switches. The main panel’s breaker serves as the disconnect for the subpanel. However, local codes may have specific requirements, so it’s essential to check with local authorities and an electrician.

Can I put 2 100 amp breakers in a 100 amp panel?

In most cases, a 100-amp panel is designed to accommodate only a single 100-amp main breaker. Adding two 100-amp breakers would likely exceed the panel’s capacity and may not be allowed by the manufacturer or local codes. Consult with an electrician for guidance.

What wire to buy for subpanel?

The wire size for a subpanel depends on its amperage rating and the distance from the main panel to the subpanel. Consult with a qualified electrician to determine the appropriate wire size for your specific installation.

Can you have a 100 amp sub panel with a 100 amp service?

Yes, you can have a 100-amp subpanel connected to a 100-amp service, as long as the subpanel’s total load does not exceed its 100-amp rating. The subpanel should be sized appropriately for the circuits it will serve.

Can I run a 100 amp sub panel off 100 amp main?

Yes, you can run a 100-amp subpanel off a 100-amp main panel, as long as the subpanel’s total load does not exceed its 100-amp rating. The subpanel should be properly sized for the circuits it will supply.

Can I run a subpanel off another subpanel?

Yes, you can run a subpanel off another subpanel, creating a sub-subpanel arrangement. However, it’s important to ensure that the total load of all subpanels does not exceed the capacity of the main panel or the panel they are connected to.

How far can a subpanel be from the main panel?

The allowable distance between a subpanel and the main panel can vary based on local electrical codes and the specific installation requirements. In many cases, subpanels are located in close proximity to the main panel, often within the same structure. Consult local codes and an electrician for precise guidance.

Can you add a subpanel if the main panel is full?

If the main panel is full and cannot accommodate additional circuits or breakers, you may still be able to add a subpanel to expand your electrical capacity. This would involve adding a subpanel with its own circuits and breakers, connected to the main panel through a feeder circuit.

Can I run a 60 amp sub panel off 100 amp main?

Yes, you can run a 60-amp subpanel off a 100-amp main panel, as long as the subpanel’s total load does not exceed its 60-amp rating. The subpanel should be sized appropriately for the circuits it will supply.

Can a 70 amp breaker feed a 100 amp sub panel?

In most cases, it is not recommended to use a 70-amp breaker to feed a 100-amp subpanel. The breaker should be appropriately sized to protect the wiring and equipment. It’s generally safer to use a breaker that matches the subpanel’s amperage rating.

Can I run a 60 amp breaker to 100 amp subpanel?

It is generally not recommended to use a 60-amp breaker to feed a 100-amp subpanel. The breaker should match or exceed the subpanel’s amperage rating to provide proper protection for the circuits. Using a 100-amp breaker or fuse for a 100-amp subpanel is typically the appropriate choice.

Should ground and neutral be separate in subpanel?

Yes, in a subpanel, the ground and neutral conductors should be kept separate. This means that there should be a separate grounding bar and a separate neutral bar in the subpanel. The neutral bar should be bonded to the panel’s enclosure, while the grounding bar should be connected to the panel’s grounding electrode system. This separation helps ensure proper grounding and reduces the risk of ground loops.

Why does a subpanel need 4 wires?

A subpanel needs four wires to provide a safe and functional electrical connection. These four wires typically include two hot (phase) conductors, one neutral conductor, and one equipment grounding conductor. This configuration allows for the safe distribution of electricity, proper grounding, and protection against electrical faults.

Can I feed a sub panel with aluminum wire?

Yes, you can use aluminum wire to feed a subpanel. However, it’s important to choose the correct size of aluminum wire based on the subpanel’s amperage rating and the length of the run. Consult with a qualified electrician to ensure that you select the appropriate size of aluminum conductors.

How far can a disconnect be from a panel?

The maximum allowable distance between a disconnect switch (such as a main disconnect) and the electrical panel it serves can vary depending on local codes and the specific installation. In many cases, it is recommended that the disconnect switch be located in close proximity to the panel, often within sight of the panel.

What is the 2 6 disconnect rule?

The “2-6 disconnect rule” is a common reference in electrical installations, but it can have different interpretations depending on context. It may refer to the requirement that no more than six disconnect switches or circuit breakers should be grouped together and that no more than two of them should be used for appliances or equipment that are not part of the same system or unit.

Do you need a disconnect for 200 amp service?

Yes, a 200-amp service typically requires a main disconnect switch or breaker as part of the service entrance equipment. This disconnect is used to disconnect power from the entire service and is often located at the service entrance point.

How do you size a sub panel?

To size a subpanel, you need to consider the total electrical load that it will serve. Calculate the amperage of the circuits you plan to connect to the subpanel, and then choose a subpanel with an amperage rating that exceeds this total load. It’s important to consult with a qualified electrician for a precise sizing calculation.

What happens if I have a 200 amp electrical service and I for more than that?

If you consistently draw more current than your 200-amp electrical service can provide, you risk overloading the system. This can lead to overheating, tripped breakers, and other electrical problems. To avoid these issues, it’s essential to manage your electrical loads and consider upgrading your service if necessary.

What is the largest sub panel from a 200 amp service?

The size of the largest subpanel that can be installed on a 200-amp service will depend on the available capacity and the specific needs of the installation. Subpanels with ampere ratings of 100, 125, or 150 amps are common choices for residential applications connected to a 200-amp main panel.

Can you use a load center as a sub panel?

Yes, a load center can be used as a subpanel. A load center is essentially an electrical panel that can serve as either a main panel or a subpanel, depending on its application and how it is configured.

Does a sub panel need a feeder breaker?

A subpanel typically does not require a feeder breaker if it is being fed directly from the main panel, and the total number of circuits or breakers in the subpanel does not exceed the main panel’s limit. The main panel’s breaker provides overcurrent protection for the subpanel’s feeder circuit.

How do I know if my 200 amp panel is overloaded?

You can determine if your 200-amp panel is overloaded by monitoring your electrical usage and checking for signs of overloading, such as tripped breakers, flickering lights, or excessive heat at the panel. If you frequently experience these issues or suspect overloading, consult with an electrician to assess and address the problem.

What size of conduit do I need for a 200 amp service?

The size of conduit needed for a 200-amp service will depend on the number and size of conductors being pulled through the conduit. In most cases, a minimum of 2-inch conduit is recommended for a 200-amp service. However, consult with an electrician to ensure compliance with local codes and specific installation requirements.

How many sub panels can you have on a 200 amp service?

The number of subpanels that can be installed on a 200-amp service depends on the total electrical load of the subpanels and the main panel’s capacity. It’s essential to ensure that the total load of all subpanels does not exceed the main panel’s 200-amp rating. Consult with a qualified electrician to determine the maximum number of subpanels you can add.

What size wire for 100 amp service 200 feet underground?

For a 100-amp service running 200 feet underground, you would typically need copper wire sized at least 3/0 AWG or aluminum wire sized at least 2/0 AWG for the service entrance conductors. However, consult local codes and an electrician for precise sizing based on your specific installation.

What size wire do I need to run 50 amps 100 feet?

To run 50 amps over a distance of 100 feet, you would typically need copper wire sized at least 6 AWG or aluminum wire sized at least 4 AWG. This is a general guideline, so consult with an electrician for precise sizing based on your specific installation.

What size wire do I need to run 40 amps 100 feet?

To run 40 amps over a distance of 100 feet, you would typically need copper wire sized at least 8 AWG or aluminum wire sized at least 6 AWG. However, consult local codes and an electrician for precise sizing based on your specific installation.

Do you need 2 or 3 wire for sub panel?

A subpanel typically requires three wires: two hot (phase) conductors and one neutral conductor. Additionally, you will also need a grounding conductor, which makes a total of four conductors when connecting a subpanel.

Can I upgrade to 200 amp service myself?

Upgrading to a 200-amp service is a complex electrical project and is typically not recommended as a DIY project. It involves significant electrical work, obtaining permits, and ensuring compliance with local codes. It’s safer and more reliable to have a licensed electrician handle the upgrade.

How many 50 amp breakers can I put in a 100 amp panel?

In a 100-amp panel, you can typically have multiple 50-amp breakers, but the exact number will depend on the specific panel’s design and the total load it’s rated to handle. As a rough estimate, you might have space for 2-4 double-pole 50-amp breakers in a 100-amp panel.

Can you run a 100 amp sub panel off of a 200 amp service?

Yes, you can run a 100-amp subpanel off a 200-amp service, as long as the subpanel’s total load does not exceed its 100-amp rating. The subpanel should be properly sized for the circuits it will supply.

How much does it cost to convert 100amp to 200amp service?

The cost to convert from a 100-amp to a 200-amp service can vary widely depending on factors such as location, existing wiring, and labor costs. As a rough estimate, it could cost anywhere from $1,500 to $4,000 or more.

How much does it cost to go from 100 amp to 200 amp?

The cost of upgrading from a 100-amp to a 200-amp service can vary based on location and specific circumstances, but it generally ranges from $1,500 to $4,000 or more.

Is it worth upgrading to 200 amp service?

Upgrading to a 200-amp service can be worth it if your electrical demands have increased or if you plan to add more circuits and appliances to your home. It provides more capacity for future growth and can improve the overall performance of your electrical system.

Is 200 amp service better than 100 amp?

A 200-amp service is generally better than a 100-amp service for homes with higher electrical demands. It provides more capacity to support additional circuits, appliances, and equipment, which can improve the convenience and safety of your electrical system. However, the choice between 100-amp and 200-amp service depends on your specific needs and circumstances.

What is the 120% rule for breaker panels?

The 120% rule in breaker panels refers to the practice of calculating the maximum allowable circuit load based on the panel’s rating. It allows you to load a panel up to 120% of its rating, but not beyond that, to account for occasional peak loads and to prevent overloading.

How many 20 amp breakers can you have on a 100 amp service?

The number of 20-amp breakers you can have on a 100-amp service depends on the total load of the circuits and appliances connected to those breakers. As a rough estimate, you might have space for around 15-20 circuits with 20-amp breakers on a 100-amp service, but it can vary based on specific requirements.

Should I use a ground rod on a sub panel?

Yes, a subpanel should typically have its own grounding rod or electrode. This grounding rod is essential to provide a safe and effective ground for the subpanel’s circuits. Proper grounding is a critical safety feature in electrical systems.

What is the code for grounding a sub panel?

The specific electrical code requirements for grounding a subpanel can vary by jurisdiction, but it generally involves installing a separate ground bar in the subpanel, connecting it to the panel’s enclosure, and ensuring that it is bonded to the main panel’s grounding system. Local electrical codes should be consulted for precise requirements.

Why don’t you ground a subpanel?

You do ground a subpanel, and it is a necessary safety measure in electrical systems. Proper grounding helps dissipate electrical faults, protects against electrical shocks, and ensures the safe operation of the subpanel and connected circuits.

How many ground rods for a 100 amp sub panel?

The number of ground rods required for a 100-amp subpanel can vary based on local electrical codes and soil conditions. In some cases, two ground rods may be recommended, spaced a certain distance apart, to ensure a proper ground connection. Consult local codes and an electrician for guidance.

Can I tie the neutral and ground together?

In a main panel (such as the main service panel), the neutral and ground should be bonded (connected) together. However, in a subpanel, the neutral and ground must be kept separate to prevent the creation of ground loops and to ensure safety. It is essential to follow this separation of neutral and ground in subpanels to meet electrical code requirements.

Can you put neutral and ground wires on the same bus in sub-panel?

No, you should not put neutral and ground wires on the same bus in a subpanel. In a subpanel, there should be separate bus bars for the neutral and grounding conductors. The neutral bus should be bonded to the panel’s enclosure, while the ground bus should be isolated and not bonded to the enclosure to prevent ground loops.

Can I have a 200 amp sub panel on a 200 amp main?

Yes, you can have a 200-amp subpanel connected to a 200-amp main panel. The subpanel should be sized appropriately for the circuits it will serve and must not exceed the capacity of the main panel.

Can I connect a 100A subpanel to a 100A main panel?

Yes, you can connect a 100-amp subpanel to a 100-amp main panel, as long as the subpanel’s total load does not exceed its 100-amp rating. The subpanel should be properly sized for the circuits it will supply.