Your main panel is full. You need more circuits. Maybe you added a workshop, converted a garage, built an accessory dwelling unit, or you’re running an EV charger that demands its own dedicated feed. Whatever the reason, a second 200-amp breaker box — called a subpanel — is often the right answer. But this project is different from swapping out a single breaker or adding a circuit. You’re tapping the main panel to feed an entirely separate enclosure, and that carries real stakes.

This post covers what that installation actually looks like, what decisions you’ll need to make before a single wire is pulled, and where the project is likely to go sideways if you aren’t careful.

What a Second 200 Amp Panel Actually Does?

A second breaker box doesn’t give you a second service entrance. Your utility still delivers power to one meter, and that feeds your main panel. The second panel draws its power from breakers inside that main panel — specifically, a double-pole breaker (or tandem breakers) that serves as the feeder breaker. From there, a feeder cable or conduit run carries power to the new subpanel.

The subpanel then acts as its own distribution point. You can run 20, 30, or 40 circuits off it depending on the box size and your load. It has its own neutral bar and its own grounding system, but those must be kept separate — unlike the main panel, where neutral and ground are bonded together. That’s one of the most common mistakes on these projects, and it causes ground faults, tripped breakers, and safety hazards.

A 200-amp subpanel is a large installation. It’s typically used when you’re powering a detached structure, a large addition, or a commercial-style setup in a residential building. Not every main panel can support feeding a full 200 amps to a subpanel — the main panel itself may only be 200 amps total, which means you’d be dedicating your entire service to the sub, with nothing left for the rest of the house.

Checking Your Main Panel Before You Commit

Before any physical work begins, open your main panel and take stock. Look for available breaker slots. You’ll need two adjacent slots for a double-pole breaker, typically 60 to 100 amps minimum for a meaningful subpanel feed (a full 200-amp feed requires 200-amp capacity in the main, plus enough headroom for your existing loads). The National Electrical Contractors Association recommends calculating your total load before sizing any feeder circuit — this isn’t just paperwork, it determines whether your existing service can physically handle the addition.

If your main panel is already running close to capacity, you may need to look at load shedding, upgrading the main service, or rethinking how much you’re asking the subpanel to carry. An electrical panel installation professional can pull your load calculations and tell you what’s feasible without guesswork.

Also check the age of your main panel. If it’s older than 25 years, this project is a good opportunity to have it inspected. Feeding a new subpanel off a degraded main panel is like putting a new roof on a crumbling foundation.

The Feeder Wire: Size Matters More Than You Think

The wire connecting your main panel to the subpanel is called the feeder. For a 200-amp subpanel, you’ll typically need 2/0 AWG aluminum or 1/0 AWG copper wire for each hot leg, plus a neutral and a separate ground. Aluminum is standard here — it’s code-compliant for feeders and significantly cheaper than copper at this gauge. According to the Independent Electrical Contractors, using undersized feeder wire is one of the leading causes of overheating and fire risk in subpanel installations.

The distance between the two panels matters. Longer runs mean more voltage drop, which means you may need to upsize the wire to maintain acceptable voltage at the subpanel. A general rule is to calculate voltage drop at no more than 3% for branch circuits and 5% total from service entrance to the last outlet. For a 100-foot run at 200 amps, you’re looking at wire that costs several hundred dollars just for the feeder — this is not a project where cutting corners on materials pays off.

If the panels are in separate buildings, the feeder typically runs through underground conduit. Trenching, conduit material, burial depth (typically 24 inches for rigid conduit under NEC 2023 guidelines, which Nevada follows as of 2026), and proper sealing at both ends all add to the scope. Wiring installation for underground runs requires the right conduit type — PVC Schedule 40 or 80, or rigid metal conduit depending on the application.

Permits and Inspections in Nevada in 2026

This is where many DIY projects run into serious problems. In Reno and Sparks, a 200-amp subpanel installation requires a permit from the local building department. As of 2026, Washoe County and the City of Reno both require electrical permits for any new panel installation, feeder installation, or service upgrade. The permit triggers an inspection, and the inspection confirms the work meets the current edition of the NEC, which Nevada has adopted with local amendments.

Pulling a permit isn’t just legal compliance — it protects you. If you sell your home and an unpermitted subpanel shows up during inspection, you’ll either need to retroactively permit it (which requires tearing into walls) or disclose it as an unpermitted alteration. The Occupational Safety and Health Administration maintains clear guidance on why permitted electrical work matters for safety, and insurance companies are increasingly denying claims on losses tied to unpermitted electrical work.

A licensed electrician can pull the permit on your behalf and schedule the inspection. That’s part of what you’re paying for when you hire a professional, and it removes the liability from your shoulders.

The Physical Installation: What the Work Looks Like

Once permits are in hand, the installation sequence typically goes like this. First, the feeder breaker is installed in the main panel. The main panel must be de-energized for this step — which in many cases requires the utility to pull the meter. This is not optional and not a step homeowners can safely skip. The Electrical Association consistently emphasizes that working on energized main lugs is one of the most dangerous tasks in residential electrical work.

With the feeder breaker in place, the feeder cables are run to the new panel location. If it’s in the same building, this may run through conduit in a basement or attic. If it’s a detached structure, it goes underground. The new panel enclosure is mounted to the wall, the feeder wires are landed on the main lugs of the subpanel, and the neutral and ground bars are kept separate — again, this separation is required and critical.

Branch circuit wiring is then run from the subpanel to each outlet, appliance, or fixture. For a new garage or workshop, this might include 20-amp general purpose circuits, a 30 or 50-amp circuit for a welder or compressor, and a dedicated circuit for an EV charger. Speaking of which, EV charging station installation is one of the most common reasons homeowners in the Reno-Sparks area are adding subpanels right now, as Level 2 chargers draw 40 to 50 amps continuously and need their own dedicated circuit.

After all wiring is complete, the work is inspected by the authority having jurisdiction. The inspector checks wire sizing, breaker ratings, proper neutral-ground separation, proper grounding electrode conductor installation, and labeling. Once approved, the utility reinstalls the meter and the new system is energized.

When to Call a Professional?

If you’ve read this far and you’re confident in your skills, you should also be honest with yourself about the scope. This isn’t a project with a forgiving margin for error. Miswired feeders, improperly bonded neutrals, and undersized wire don’t always fail immediately — they fail under load, often at the worst possible time. The National Electrical Contractors Association reports that electrical fires cause over $1.5 billion in property damage annually in the United States, and subpanel installation errors are a documented contributing factor.

Ohms Electric Reno & Sparks handles this type of project regularly. Their team understands local permit requirements, utility coordination, and the specific load demands that come with Northern Nevada homes — from older homes in Midtown Reno to new construction in Spanish Springs. If you’re also adding outlets, lighting, or other electrical work to the new space, those can typically be bundled into the same project. Check out their circuit breaker installation services for more on what professional installation includes, and their full services page for a broader look at what they offer.

If you run into a breaker that keeps tripping or suspect your existing panel has issues before you add a subpanel, Northern Nevada circuit breaker repair is a good first call to make sure the foundation is solid before you build on it.

Take the Next Step

A second 200-amp breaker box done right gives you reliable, safe power for decades. Done wrong, it creates fire risk, fails inspection, and costs more to fix than it would have cost to do correctly the first time.

If you’re planning this project in the Reno or Sparks area and want an honest assessment of what it will take — including load calculations, permit scope, and a realistic cost estimate — contact us at Ohms Electric. Or visit their circuit breaker installation page to learn more and request a consultation. Get the work done right, get it permitted, and get it inspected. That’s the only version of this project worth doing.