04 Jun
The Short Answer
Yes, a single electrical panel can absolutely run out of space, and when it does, adding a subpanel is one of the most practical ways to expand capacity without replacing the entire main panel. A subpanel draws power from the main panel through a dedicated breaker and distributes it to a separate set of circuits, usually in a garage, workshop, or home addition.
Why Homeowners End Up Needing a Subpanel
Most homes built in the mid-20th century came with 100-amp or 150-amp panels that had enough breaker slots for the electrical loads of that era. Nobody was running EV chargers, whole-home air conditioning systems, and home offices with multiple workstations back then.
Fast-forward to today, and those older panels are frequently maxed out. Every slot is filled, yet the demand for new circuits keeps growing. Palos Hills has a large stock of homes from the 1960s and 1970s, and this is one of the most common issues electricians see in the area.
When a Subpanel Makes Sense
A subpanel installation is often the right call in a few specific situations. If you are finishing a basement or adding a garage, running individual circuits all the way back to the main panel can be expensive and messy. A subpanel placed close to the new space cuts down on wire runs significantly. It also makes future work easier since any new circuits start at the subpanel rather than requiring a trip back to the main panel.
Detached structures are another strong candidate. A detached garage or a backyard workshop needs its own grounding system and typically benefits from a subpanel rather than a long individual circuit. The same applies to anyone installing a Level 2 EV charger, which usually requires a dedicated 50-amp or 60-amp circuit that may not fit in a crowded main panel.
What a Subpanel Cannot Fix
A subpanel does not increase the total amperage coming into your home. If your main service is 100 amps and your household demand is already pushing close to that limit, adding a subpanel will not solve the underlying capacity problem. In that case, a full panel upgrade to 200 amps is usually the right move first. An electrician can run a load calculation to tell you which situation you are actually in before any work begins.
What Goes Into the Installation
The process is more involved than it might look from the outside. A licensed electrician will size the feeder wire correctly based on the amperage of the subpanel, which typically runs between 60 and 100 amps for residential use. Undersized wire is a fire risk and will fail an inspection.
Permits and Code Requirements
In Illinois, subpanel work requires a permit and inspection. This is not optional paperwork. The inspection confirms that the feeder breaker in the main panel is sized correctly, that the subpanel has a proper neutral-ground separation (subpanels require a separate ground bar, unlike main panels), and that all connections are tight and correctly rated. Skipping the permit might save a few dollars upfront but creates real problems when you go to sell the home or file an insurance claim.
Local residents who have already upgraded to a 200-amp service are well-positioned for a subpanel addition since there is usually headroom in the main panel to accommodate a properly sized feeder breaker. If you are not sure what your current service looks like, an electrical inspection can give you a clear picture before committing to any work.
For homeowners in the southwest suburbs who are also thinking about adding an EV charger alongside a subpanel, the two projects pair well together. Check out the options for EV charger installation in Orland Park to see what that kind of work typically involves nearby.
Related Questions
How many circuits can a subpanel handle?
That depends on the size of the subpanel you install. A common residential subpanel has between 6 and 24 slots, with 12-slot and 24-slot panels being the most popular choices. Each slot holds one single-pole breaker (120V) or one double-pole breaker (240V), so a 24-slot panel can theoretically support 24 circuits, though real-world installations rarely fill every slot right away.
Is it safe to have a subpanel right next to the main panel?
Yes, physically placing a subpanel next to the main panel is perfectly acceptable and actually pretty common in basements where space allows. The key requirement is that the neutral and ground buses must remain separate in the subpanel, even though they are bonded together at the main panel. This is a code requirement under the National Electrical Code (NFPA 70) and exists to prevent stray current from traveling on ground wires. A licensed electrician familiar with Illinois permit requirements will handle this correctly from the start.