The request usually starts the same way. A homeowner in Wheeling or Des Plaines finishes a garage, adds a workshop, or converts a basement, and suddenly there are three circuits doing the work of eight. Lights dim when the compressor kicks on. A space heater trips a breaker every January morning. Somewhere there is an extension cord doing something it was never designed to do.
The fix is a sub-panel: a smaller distribution panel fed from your main service, giving the new space its own breakers close to where the loads are. Done right, it is one of the highest-value electrical projects in a house. Done wrong — and we see it wrong often — it is a genuine shock and fire hazard hiding behind a closed cover.
What a Sub-Panel Is (and What It Is Not)
A sub-panel is fed by a single breaker in your main panel and distributes that capacity to branch circuits in another location. It does not add capacity to your electrical service. If your home has a 100-amp service that is already near its limit, a sub-panel simply relocates the problem. That distinction matters, and any electrician who does not run a load calculation before quoting you is guessing.
The Code Details That Separate a Good Install From a Dangerous One
Four-wire feeders, always
A sub-panel must be fed with four conductors: two hot, one neutral, one equipment ground. Inside the sub-panel, the neutral bar must be isolated from the enclosure and the ground bar bonded to it. The bonding screw or strap that ships in the panel gets removed. When neutrals and grounds are landed together in a sub-panel, normal return current flows on the ground path and on any metal — conduit, ductwork, water piping — that connects the two buildings. This is the single most common defect we find in DIY and handyman sub-panels.
Detached buildings need their own grounding electrode
Feeding a detached garage or shop means installing a grounding electrode system at that structure — typically two ground rods bonded to the sub-panel ground bar. The feeder ground does not substitute for it.
Disconnecting means and working clearance
Detached structures require a disconnecting means at the building. Every panel needs 30 inches of width, 36 inches of depth, and 6.5 feet of headroom kept clear. A panel behind shelving or above a workbench fails inspection and makes future service dangerous.
Wire, conduit, and burial depth
Underground feeders to a detached building are usually direct-burial USE/UF cable or conductors in PVC conduit. Burial depth depends on wiring method and whether the circuit is GFCI-protected — typically 18 to 24 inches for residential branch circuits and feeders. In frost-heave country, deeper is better than the minimum.
GFCI and AFCI requirements
Current code requires GFCI protection for garage, basement, and outdoor receptacles, and AFCI protection for most habitable-room circuits. A modern sub-panel install brings the new space up to those standards.
Sizing: How Many Amps Do You Actually Need?
| Use Case | Typical Sub-Panel Size | Notes |
|---|---|---|
| Finished basement, lighting and receptacles | 60 amp | 8–12 circuits is usually plenty |
| Attached garage with opener, lights, outlets | 60 amp | Add capacity if you plan a heater |
| Heated garage or workshop with 240V tools | 100 amp | Table saw, dust collector, compressor, heater |
| Detached garage plus Level 2 EV charger | 100 – 125 amp | EVSE alone can be a 60A circuit |
| Addition with its own HVAC and kitchenette | 100 amp | Load calc required |
| Welding or serious machine shop | 125 – 150 amp | Duty cycle drives the number |
Sizing up at install time is cheap; coming back later is not. The difference between 60-amp and 100-amp feeder wire on a 60-foot run is a small fraction of total job cost.
What Sub-Panel Installation Costs in Wheeling & Des Plaines
| Scenario | Typical Installed Cost |
|---|---|
| 60-amp sub-panel, same building, short feeder run | $1,200 – $1,900 |
| 100-amp sub-panel, basement or attached garage | $1,600 – $2,800 |
| 100-amp sub-panel, detached garage (trenching included) | $2,800 – $5,500 |
| Add-on: 200-amp main panel upgrade first | $2,400 – $4,500 |
| Add-on: Level 2 EV charger circuit from new sub-panel | $450 – $1,100 |
| Add-on: trenching under a driveway (bore or cut/patch) | $900 – $3,000 |
Costs include permit and inspection. Trenching length, driveway crossings, and whether the main panel has a spare double-pole slot are the biggest swing factors. Sunbit and PowerPay financing is available if you would rather spread the cost.
Do You Need a Main Panel Upgrade First?
Run the math before you commit. A standard load calculation totals your general lighting load, appliances, HVAC, and any new loads, then applies demand factors. Signs you likely need a service upgrade before adding a sub-panel:
- 100-amp service with central air, electric dryer, and electric range already installed
- No open double-pole slots and no room for tandems
- Federal Pacific Stab-Lok or Zinsco panel — these should be replaced regardless
- Plans that include a heat pump, EV charger, or electric water heater in the next few years
If a heat pump is anywhere in your plans, do the panel upgrade and sub-panel as one project. Combining them saves a second permit, a second mobilization, and often a second drywall repair.
Permits and Inspections
Both Wheeling and Des Plaines require an electrical permit for sub-panel installation, and both require the work to be performed by a licensed electrical contractor registered with the village. Inspections generally happen in two stages on a detached-building job: an open-trench inspection before backfill, and a final inspection after termination. Skipping the permit is a bad trade — unpermitted panel work shows up in home inspections and can hold up a sale.
Frequently Asked Questions
Can I feed a sub-panel with three wires like older installs?
No. Three-wire feeders to sub-panels are no longer permitted. Existing three-wire feeders to detached buildings are grandfathered only in limited situations, and we recommend correcting them.
How long does the job take?
A same-building sub-panel is typically one day. A detached garage with trenching is usually two days plus inspection scheduling.
Can the sub-panel go outside?
Yes, with a NEMA 3R rated enclosure. Indoor placement is preferred where practical for serviceability.
Will this fix my flickering lights?
If flickering comes from overloaded shared circuits, yes. If it is service-side — loose neutral, utility issue, failing main lugs — a sub-panel will not help, and that condition needs immediate attention.
Can you add a sub-panel and an EV charger at the same time?
That is one of the most common combinations we install, and doing them together is significantly cheaper than sequentially.
Talk to a Licensed Electrician
MMDS handles sub-panels, circuits and wiring, panel upgrades, and EV charger installation across Wheeling, Des Plaines, and the surrounding suburbs. We run the load calculation first and tell you honestly whether you need a service upgrade or just a sub-panel.
Call (847) 221-6280 or request a quote. Ask about Sunbit and PowerPay financing.