A home’s electrical system is like its central nervous system. It powers all the critical appliances and devices that modern families rely on daily. As families grow and homes are renovated, more electrical circuits get added. At some point, the main electrical panel may not have enough space for additional circuits. This is when homeowners need to consider installing a subpanel.
A subpanel, also called a sub distribution panel, is an additional electrical panel that “branches off” from the main service panel. It provides extra circuit capacity so you can add more circuits to power additional lights, outlets, and appliances. Installing a subpanel is a complex job that requires an electrician, permits, and following electrical codes. However, it brings many benefits that make it a worthwhile home upgrade.
Why Homes Need Subpanels
There are several common triggers that indicate a home needs a subpanel:
- Insufficient Circuits – The main panel may be full which prevents adding lighting, outlets, or appliances. A subpanel adds more circuits.
- Home Additions – Home expansions like adding a bedroom or basement often require running new wiring. Rather than overload the main panel, circuits can be added to a subpanel.
- Major Appliance Upgrades – New high wattage appliances like HVACs and hot tubs need dedicated circuits which may overload the capacity of an older main panel.
- Electrical Repairs – Upgrading to a grounded electrical system or replacing faulty wiring can require a subpanel to add more circuits.
- Safety Issues – Outdated panels with fuses or insufficient amperage may need to be upgraded for safety by installing a subpanel.
- Modernization – Upgrading to modern arc-fault and ground-fault circuit interrupter (GFCI) outlets may require installing AFCI/GFCI breakers which need extra space in a subpanel.
- Pool Installation – Pools require dedicated high voltage circuits for pumps, lighting, chlorinators, etc. A subpanel simplifies adding these specialized circuits.
If your home’s main panel is out of circuit space, can’t support added load, or needs electrical upgrades, a subpanel is the solution.
Benefits of Installing a Subpanel
Adding a subpanel brings many benefits:
More Circuit Capacity
The main advantage of a subpanel is installing more circuits. This allows:
- Adding extra lighting and power outlets
- Running new wiring for home additions and renovations
- Adding high wattage appliances like EV chargers or HVACs
- Adding dedicated circuits for pools, hot tubs, and outbuildings
- Converting 2-wire circuits to safer and more modern grounded circuits
With a subpanel’s extra capacity, homes can be updated and customized to modern electrical needs.
Improved Safety
Subpanels let homeowners upgrade outdated electrical systems which improves safety:
- Replacing fuse boxes with circuit breakers reduces fire risk
- Grounded circuits reduce risk of shocks and electrocution
- GFCI and AFCI circuits help prevent fires and electrocution
- Higher amperage panels safely support larger electrical loads
By allowing upgrades, subpanels bring electrical systems up to modern safety standards.
Added Property Value
Upgraded electrical service and ample power availability make homes more attractive to buyers. This increases property values and resale potential.
More Convenient Access
Main panels are often in inconvenient locations like basements or closets. Additional subpanels can be installed in utility rooms or garages providing easier access for homeowners to reset tripped breakers.
Flexibility for Electrical Customization
Subpanels allow customization like:
- Independent control circuits for detached structures
- Dedicated circuits for appliances, computers, home theater
- Isolating high draw equipment like HVACs on separate circuits
- Adding generator transfer switches to subpanels for backup power
For custom electrical needs, subpanels provide flexibility that main panels lack.
Cleaner Organization
Subpanels allow reorganizing circuit locations, types, and labels for a neater and more organized setup compared to cramped main panels.
Cost Savings
Adding circuits to an existing subpanel is inexpensive compared to upgrading the main panel which requires replacing the main feeder wires and relocating the outside meter/main disconnect.
Overall, subpanels provide homeowners with options to expand and customize their electrical system in ways that a single main panel does not. The benefits subpanels offer make them a popular upgrade for modern homes.
Subpanel Basics
Electrical subpanels have the same basic design and components as main panels. However, there are some key differences.
Power Source
The main service panel is fed power directly from the utility company meter and service wires. Subpanels are connected to and get their power from a circuit in the main panel called a sub-feed or subpanel feeder.
Main Disconnect
The main panel includes the master shutoff called the “main disconnect” which cuts power from the utility service wires to the entire electrical system. Subpanels don’t have main disconnects; they share the main panel’s main disconnect.
Breakers
Like main panels, subpanels use either fuses or circuit breakers to protect circuits from overloads. Most modern subpanels use breakers. The subpanel breakers control only the circuits located in the subpanel itself.
Grounding
Main panels include the grounding system and connection point for the ground wires. Subpanels don’t have their own grounding system. They continue the main panel’s grounding method.
Locations
While main panels are usually centrally installed, subpanels can be installed anywhere they are needed like in detached garages, basements, or utility closets.
Connections
Main panels connect to the outdoor service wires coming in from the meter and utility transformer. Subpanels are installed indoor and connect to the main panel through wires in the home’s conduit.
While subpanels function similar to main panels, key differences exist in their power source, disconnects, grounding, and connections back to the main panel.
Subpanel Installation
Subpanels should be installed by licensed electricians following proper procedures and local codes. Improper installation can create serious hazards. The basic steps include:
1. Planning
- Determine subpanel location – Garages, basements, and utility rooms are common locations
- Select subpanel size – 100 amps is typical for small homes. Larger homes may need 200 amp or more.
- Choose a subpanel main breaker amperage that matches the ampacity of the feeder wires
- Select a feeder wire size able to safely handle the subpanel’s total load
- Plan circuit locations – lightning, outlets, appliances etc.
2. Mounting
- Mount the subpanel enclosure securely to studs or rigid mounting blocks
- Ensure proper clearances to other objects and surfaces
3. Wiring
- Run conduit and cables from main panel to subpanel location
- Pull the feeder wires through conduit from main panel to subpanel
- Connect neutral and ground wires and bus bars in the subpanel
- Connect feeder wires to subpanel main breaker/lugs
4. Connections
- Connect circuits breakers and run wiring to circuits
- Label and organize all circuits and breakers
- Attach cover plate and close subpanel enclosure
5. Testing & Inspection
- Use a digital multimeter to test voltages and continuity
- Inspect grounding, cable sizes, connections, and splices
- Check for secure mounting and covers
- Have inspected by the Authority Having Jurisdiction (AHJ) to get approval
Proper planning, materials, cable sizing, overcurrent protection, grounding, and installation are vital for a safe subpanel.
Choosing a Subpanel Location
The subpanel location depends on a home’s layout, the position of the main panel, and proximity to new circuit wiring:
- Basements – Basement subpanels easily connect to upstairs or outdoor circuits. However, accessibility may be difficult with finished basements.
- Garages – Garage subpanels simplify wiring to outdoor circuits. They allow quick access without going inside the home.
- Laundry/Utility Rooms – Like garages, utility room subpanels provide convenient indoor access without going to the basement.
- Workshops – For home workshops, a subpanel nearby provides easy access to reset tripped breakers.
- Roof Access – For new rooftop solar systems, a subpanel near the roof access simplifies running conduit up to the solar panels.
- Adjoining Rooms – Avoid locating subpanels in rooms with hazardous areas like bathrooms, kitchens, or bedrooms if possible. However, placing subpanels in closets in these rooms is sometimes necessary.
- Detached Buildings – For wiring standalone structures like sheds and garages, a separate subpanel in each building provides convenient control and access.
Consider existing and planned circuit locations, accessibility, and proximity to the main panel when choosing the optimal subpanel location.
Subpanel Size & Circuit Capacity
Subpanels are available in a range of standard amperage sizes:
- 60 amps
- 70 amps
- 100 amps
- 125 amps
- 150 amps
- 200 amps
100 amp subpanels are typical for average homes. The subpanel’s main breaker size must match the amp rating of the wires feeding it from the main panel called the “sub-feed wires”.
The subpanel amperage also determines its circuit capacity:
- A 100 amp subpanel can hold 20 to 40 circuits depending on the breaker sizes
- A 200 amp subpanel may have 50 to 80 circuit spaces
For homes requiring a couple dozen new circuits, a 100 amp subpanel is usually sufficient. Larger homes often need 200 amp subpanels for additional capacity.
Carefully determine how many extra circuits are needed and select the appropriately sized subpanel. An electrician can help choose the right subpanel amperage rating. Oversizing leads to waste while undersizing will require another upgrade.
Subpanel Feeder Wire Size
The subpanel feeder wires must be sized correctly to:
- Handle the total amp load of all circuits
- Prevent hazardous overheating
- Keep voltage drop within safe limits
Typical feeder wire sizes are:
- #2 AWG for 100 amp subpanels
- #3/0 AWG for 150 amp subpanels
- 250 kcmil for 200 amp subpanels
The required wire size increases for longer wire runs between the main and subpanel. Professional electricians use advanced National Electrical Code (NEC) calculations to determine the optimal wire size.
Undersized feeder wires can dangerously overheat or even melt. Oversized wires waste money. Properly sized wires ensure electrical safety and efficiency.
Subpanel Feeder Wiring
The subpanel must connect to the main panel through thick, high capacity feeder wires:
- Feeder wire types are single conductors or UF cable (underground feeder cable)
- Wires are run through metal conduit for safety and protection
- Conduit also simplifies pulling the wires to the subpanel
Subpanels use either three or four feeder wires:
Three Wire Feeders
- Two hot wires (120 volts each)
- One shared neutral
Four Wire Feeders
- Two hot wires
- One neutral wire
- One ground wire
While separate neutral and grounding wires are safer, code allows shared neutrals on feeders under limited circumstances.
Properly running conduit and thick feeder cables is demanding. This wiring task is best left to professional electricians.
Subpanel Grounding
The subpanel continues the grounding method from the main panel:
- Grounded – Has ground wires and grounding electrode connection
- Ungrounded – No ground wires, only hot and neutral
A grounded subpanel offers better protection against shocks and fires. Even if the main panel is ungrounded, it is smart to install a grounded subpanel to improve safety.
Subpanels connect to the same grounding electrodes as the main panel like the water pipe, ground rods, or UFER ground. Separate ground rods just for the subpanel are rarely allowed any more per NEC rules. Proper grounding at a subpanel ensures all circuits benefit from a solid earth ground connection.
Subpanel Circuit Breaker Types
Standard circuit breakers protect subpanel circuits from overloads. Maximum breaker sizes depend on the wire gauges used. Common residential subpanel breaker types are:
- 15 amp (lighting circuits, small appliances)
- 20 amp (outlets, kitchen circuits)
- 30 amp (electric dryer, air conditioner)
- 40 amp (electric range, water heater)
- 50 amp (electric vehicle charger, HVAC)
Larger breaker sizes may be needed for heavy loads like pool equipment or machinery.
Subpanels also allow installing advanced safety breakers like:
- AFCI – Arc Fault Circuit Interrupter – Prevents dangerous electrical arcing
- GFCI – Ground Fault Circuit Interrupter – Detects ground faults or leakage
Homeowners sometimes upgrade main panels to add AFCI and GFCI protection. Installing them in a subpanel is an easier and cheaper alternative.
Carefully labeling all subpanel breakers makes it easy to isolate issues when troubleshooting tripped circuits. Neat and logical circuit organization also improves safety.
Typical Subpanel Circuits
Subpanels allow installing circuits wherever they are needed throughout a home. Here are some typical subpanel circuit uses:
Lighting Circuits
- Extra lighting circuits for additions, renovations, or outdoor areas
- Individual lighting circuits for workshops, garages, and basements
Outlets Circuits
- Additional 15 to 20 amp outlet circuits for added rooms or renovated areas
- Individual 20 amp appliance circuits (kitchens, laundry, workshops, etc)
- Dedicated outlet circuits for computers, home theater, aquariums etc.
Major Appliance Circuits
- 240 volt circuit for an electric vehicle charger (50 amp)
- Dedicated 240 volt AC circuit (30 amp)
- Pool or hot tub equipment circuits (50 to 60 amps)
Outdoor and Garage Circuits
- Detached workshop, barn or garage lighting and outlets
- Outdoor security and accent lighting
- GFCI protected outdoor receptacles
- Welder or compressor circuits in garage workshops (30 to 50 amps)
Specialty Circuits
- Low voltage lighting transformers
- Central vacuum systems
- Backup generators and automatic transfer switches
- Solar microinverters and equipment
Subpanels provide the flexibility to add a wide variety of circuits anywhere in homes.
Cost of Installing a Subpanel
Subpanel installation costs typically range from $800 to $2500 depending on the home’s layout, complexity, and local electrician rates. Cost factors include:
- Permits – $100 to $500
- Subpanel equipment – $200 to $600
- Wire and conduit – $1 to $5 per foot
- Electrician fees – $50 to $100 per hour
- Load calculation and design fees
- Specialty circuits or upgrades
In addition to installation costs, homeowners need to budget for future expenses to add the individual circuits. However, spreading future circuit additions over time can make the total costs more manageable.
Homeowners should get quotes from at least 3 local electricians to find the best value. While subpanels require an initial investment, the ongoing benefits for home upgrades and customization make it money well spent.
DIY Subpanel Installation?
Is it possible to install a subpanel yourself as a DIY project? Technically, it is possible for homeowners with extensive electrical knowledge and experience. However, there are some major caveats:
Safety – Mistakes can lead to fires, electrocution, or even death. Proper techniques, materials, and grounding are critical.
Permits – Most areas require permitting which involves passing inspections from local electrical inspectors. They carefully check that all codes and standards have been followed.
Expertise – Sizing panels and wires along with making safe connections requires specialized knowledge and skills. Training is essential to gain competence.
Unless you are a licensed electrician or have received proper training, it is not advisable for homeowners to attempt subpanel installation themselves. The risks of safety hazards combined with not passing rigorous permitting and inspections make DIY not worthwhile except for the most experienced individuals. Hiring a professional, licensed electrician is strongly recommended for subpanel installation and wiring.
Finding an Electrician for Subpanel Installation
Here are tips for finding the best electrician for your subpanel installation:
- Get Referrals – Ask neighbors or friends for electricians they have used and trust.
- Verify Licensing – Electricians must be licensed in your state and city. Ask to see their license number.
- Check Reviews – Search online for ratings and reviews of local electricians on Google, Yelp, and Angie’s List.
- Find Experts – Search for electricians experienced in subpanels, not just general wiring.
- Get Quotes – Get quotes from 3 to 5 electricians detailing work and costs. Avoid paying just hourly fees with no cap.
- Professionalism – Choose an electrician who answers questions clearly, provides a contract, and respects your home.
- Communication – Ensure the electrician will keep you informed as the project progresses.
- Warranty – Only hire electricians who guarantee their workmanship if issues arise.
Investing the time to carefully choose the right electrician means you can be confident your new subpanel will be installed correctly and safely.
Home Insurance and Subpanels
How does adding a subpanel impact home insurance?
- Improve Coverage – Upgrading to a grounded subpanel from an older fuse panel may qualify for a discount on premiums.
- No Impact – A properly installed subpanel to code standards will not increase rates or risk.
- Added Value – Extra capacity and modern safety circuits can increase dwelling coverage amounts for replacement cost.
- Document the Upgrade – Inform