Written by Jimco Electric | Published on July 2025
A main breaker panel is the primary electrical hub that receives power from the utility and distributes it throughout your entire home. A subpanel is a secondary box that branches off the main panel to serve a specific area, like a detached garage, finished basement, or home addition.
For Chicago homeowners, understanding the difference matters a lot. Older homes in neighborhoods like Logan Square, Beverly, and the suburbs west of the city often have undersized panels that can not handle modern electrical loads without a subpanel upgrade.
This guide covers how each panel works, when you need one versus the other, what installation costs look like in the Chicago area, and what local code requires.
Understand What a Main Breaker Panel Actually Does
Your main breaker panel, also called the main electrical panel or load center, is the first point of distribution after power enters your home from the utility meter. It holds individual circuit breakers that protect each circuit in your house.
The main breaker at the top of the panel controls all power to the entire home. If you flip that breaker off, everything goes dark. Most Chicago homes built after 1990 have a 200-amp main panel. Older homes may still have 100-amp service, which is often inadequate for today’s appliances.
Key functions of the main breaker panel include:
- Receiving power directly from the utility through the meter base
- Distributing circuits for every room, appliance, and outlet in the home
- Housing the main disconnect breaker for the whole structure
- Providing overcurrent protection to prevent fires and equipment damage
- Serving as the grounding and bonding point for your electrical system
The main panel is always located inside or attached to the structure it serves. In Chicago bungalows and two-flats, you will typically find it in the basement or a utility area near the back of the building.
Understand What a Subpanel Is and How It Differs
A subpanel, sometimes called a secondary panel or distribution panel, gets its power from the main panel through a feeder circuit. It does not connect directly to the utility. Think of it as an extension of your main panel placed closer to where the power is needed.
Subpanels are common in Chicago-area homes when:
- A detached garage or coach house needs its own circuits
- A basement is being finished and needs dedicated circuits for a home theater, gym, or bedroom
- A home workshop or woodworking shop requires 240-volt equipment
- An addition or ADU (accessory dwelling unit) is added to the property
- The main panel is full and has no open breaker slots
One critical difference: a subpanel does NOT have a utility connection. It also handles grounding differently. Per the National Electrical Code (NEC), neutral and ground wires must be kept separate in a subpanel, while they are bonded together at the main panel only.
Jimco Electric frequently installs subpanels in homes throughout the western suburbs, where finished basements and detached garages are extremely common on properties built in the 1960s through 1990s.
Compare Main Panel vs Subpanel Side by Side
Use this comparison to quickly understand the functional differences between the two panel types.
| Feature | Main Breaker Panel | Subpanel |
|---|---|---|
| Power Source | Directly from utility meter | Fed from main panel via feeder |
| Main Disconnect | Yes, required | Optional (may use feeder breaker) |
| Neutral/Ground Bond | Bonded together | Kept separate (NEC requirement) |
| Typical Amperage | 100A, 150A, or 200A | 60A, 100A, or 125A |
| Location | Near utility meter entry point | Near the area being served |
| Permit Required | Yes, always | Yes, always in Illinois |
| Average Install Cost (Chicago area) | $1,500 to $3,500 | $500 to $1,800 |
Both panels require permits in Illinois. Chicago and most collar counties including Cook, DuPage, and Will require an electrical permit and inspection for any panel work. Never hire a contractor who skips the permit process.
Review Typical Costs for Panel Work in the Chicago Area
Electrical panel costs vary based on amperage, panel brand, labor rates, and whether trenching or conduit runs are needed. Here is what homeowners in Chicago and the surrounding suburbs should expect to pay in 2025.
| Service | Typical Cost Range | Notes |
|---|---|---|
| Main panel upgrade (100A to 200A) | $1,800 to $3,500 | Includes permit, inspection |
| New subpanel installation (60A) | $500 to $900 | Short feeder run, indoor |
| New subpanel installation (100A) | $900 to $1,800 | Detached garage or addition |
| Subpanel with underground feeder | $1,200 to $2,500 | Requires trenching to detached structure |
| Panel replacement (same amperage) | $1,200 to $2,000 | Old Federal Pacific or Zinsco swap |
| Permit and inspection fees (IL) | $75 to $250 | Varies by municipality |
Costs in Chicago proper tend to run slightly higher than suburban areas due to union labor requirements on certain projects and stricter city inspection processes. Suburbs like Naperville, Joliet, and Aurora typically fall in the middle of these ranges.
Jimco Electric provides upfront estimates for all panel work with no hidden fees. The price you are quoted includes permits, labor, and materials.
Know When You Need a Subpanel Instead of a Main Panel Upgrade
This is one of the most common questions homeowners ask. The answer depends on two things: how much total capacity your current main panel has, and where the new circuits need to go.
You likely need a subpanel if:
- Your main panel still has capacity (unused amps) but no open breaker slots
- You are adding circuits to a detached structure like a garage or shed
- You want to group circuits for one zone (basement, workshop) without cluttering the main panel
- The area needing power is far from the main panel and running individual circuits would be expensive
You likely need a main panel upgrade if:
- Your home still has 100-amp service and you are adding an EV charger, hot tub, or electric HVAC
- Your current panel is a known hazardous brand (Federal Pacific Stab-Lok, Zinsco, or Pushmatic)
- Breakers are tripping frequently under normal household loads
- You are adding significant square footage to the home through an addition
In some cases, you need both. A 200-amp main panel upgrade followed by a subpanel to a new garage is a common combination Jimco Electric completes regularly in the western and southwestern suburbs of Chicago.
Learn What Illinois and Chicago Code Requires for Panel Installations
Illinois follows the National Electrical Code with some state and local amendments. Chicago has its own electrical code based on the NEC but with additional city-specific requirements that differ from suburban municipalities.
Key code requirements to know:
- All panel work requires a permit. No exceptions in Chicago or any Illinois municipality.
- Only a licensed electrical contractor can pull permits in Chicago. Homeowner permits are not issued for panel work.
- Subpanels must have the neutral and ground bars isolated and not bonded together.
- Any underground feeder to a detached structure must be in conduit or use direct-burial rated cable at proper depth (typically 24 inches for conduit in Illinois frost conditions).
- AFCI and GFCI protection requirements apply to new circuits added in either panel type.
Chicago’s Bureau of Electrical Inspections conducts inspections after permits are pulled. In the suburbs, inspections are handled by each municipality or county. DuPage County and Will County both have active inspection departments with scheduling requirements.
Hiring a licensed electrician like Jimco Electric ensures your panel work is code-compliant, properly permitted, and passes inspection the first time.
FAQs on Main Breaker Panels and Subpanels
Can I add a subpanel to a 100-amp main panel?
Yes, but only if your total electrical load allows it. A 100-amp main panel running near capacity does not have enough headroom to safely feed a subpanel with meaningful amperage. An electrician should calculate your load before recommending this route. In many Chicago-area older homes, a main panel upgrade to 200 amps is the better first step.
Does a subpanel increase my home’s electrical capacity?
No. A subpanel does not add capacity to your home. It simply reorganizes and redistributes the existing capacity from your main panel. The total amperage available to your home is determined by the utility service and main panel size, not by adding a subpanel.
How far can a subpanel be from the main panel?
There is no code-specified maximum distance, but the farther the subpanel is from the main panel, the larger the feeder wire needs to be to account for voltage drop. For detached garages in typical Chicago-area lots, a 100-foot run is common and manageable with proper wire sizing. Your electrician will calculate the correct wire gauge for your specific run length and amperage.
Is a subpanel in a detached garage safe in Chicago winters?
Yes, when properly installed. The panel enclosure should be rated for the environment, and any outdoor or garage panel should be a NEMA 3R rated enclosure or better. Illinois winters put stress on electrical connections, so having a licensed electrician install the panel with proper weatherproofing is important for long-term safety.
Do I need a permit for a subpanel in Chicago?
Yes, always. Both the City of Chicago and all surrounding Illinois municipalities require a permit for subpanel installation. The work must be done by a licensed electrical contractor, inspected, and signed off before the panel is energized. Unpermitted electrical work creates liability issues when you sell your home and can void your homeowner’s insurance.
What brands of panels do electricians use in the Chicago area?
Licensed electricians in the Chicago area commonly install Square D (Homeline and QO series), Eaton, and Leviton panels. Siemens is also widely used. These brands are all NEC compliant and have good availability through local suppliers. Jimco Electric typically uses Square D QO series for its reliable breaker quality and long parts availability.
Wrap Up and Next Steps
The main breaker panel controls your entire home’s power supply, while a subpanel extends circuits to a specific area without replacing or upgrading your primary service. Knowing which one you need saves you money and ensures your electrical system is safe and code-compliant.
If you are a Chicago homeowner or live within 40 miles of the city and are not sure whether your project calls for a panel upgrade, a new subpanel, or both, Jimco Electric can assess your current system and give you a clear recommendation with a written estimate.
Call Jimco Electric at 708-304-8687 to schedule your panel consultation. We serve Chicago and communities throughout the surrounding suburbs with licensed, permitted electrical work you can count on.