Installing an EV Charger in a Detached Garage: Whats Really Involved and Why It Matters

When homeowners in Ashburn, Leesburg, or Stone Ridge call about installing an EV charger in their detached garage, I often hear the same assumption: "You already have power in the garage, so it should just be a matter of adding a charger, right?" It's a logical thought, but the reality is much different. Detached garages fall under completely different electrical code rules, and once you understand why, the scope of the work starts to make sense.

This isn't about complicating a simple job or adding unnecessary costs. It's about safety, code compliance, and creating a charging setup that works reliably for years to come. Let me walk you through what's really involved when you want to charge your EV in a detached garage.

Why Detached Garages Are Different

The National Electrical Code treats detached garages as separate structures, not extensions of your home. This distinction brings Article 225 into play, which governs how power can be supplied to separate buildings. That single classification changes everything about how EV chargers must be installed.

Most detached garages were originally wired with just a small branch circuit: enough for some lights and maybe a receptacle or two. This setup was perfectly fine when it was built, but it was never designed to handle modern electrical loads like EV chargers.

EV chargers are classified as continuous loads under NEC Article 625, meaning they're expected to run for three hours or more at a time. Because of this, the code requires the circuit supplying the charger to be sized at 125% of the charger's operating current. This is why EV chargers always need dedicated circuits and cannot legally or safely be added to existing garage wiring.

The "One Supply Rule" Changes Everything

Here's where many homeowners get surprised. Article 225 generally limits detached structures to a single electrical supply: either one feeder or one branch circuit, but not both. If your garage already has a branch circuit running from the house (which is extremely common), adding a second circuit for an EV charger would give the garage multiple supplies. In residential situations, that's typically not allowed.

This rule is the main reason installing an EV charger in a detached garage often involves more than just running a new cable. The proper, code-compliant solution usually means changing how the entire garage receives power.

Instead of feeding the garage with a single branch circuit, an appropriately sized feeder runs from your home's main panel to a subpanel inside the garage. That feeder complies with Article 225 and terminates into the garage subpanel. Once that's in place, all garage circuits: including the EV charger: are supplied from that single feeder. Existing circuits can typically be reconnected to the new panel rather than abandoned.

Understanding Feeder and Subpanel Requirements

When we upgrade a detached garage for EV charging, we're essentially treating it like a small electrical service. The feeder size depends on the total electrical load the garage will carry, including the EV charger, existing lighting, and any receptacles.

For a typical residential EV charger installation near me, we often install a 100-amp feeder with a corresponding subpanel in the garage. This provides plenty of capacity for a 50-amp EV charger circuit while leaving room for existing loads and future additions.

The subpanel installation must follow specific rules. It needs to be located as close as possible to where the feeder enters the garage, and it serves as the disconnecting means for the building. Most residential installations don't require a separate exterior disconnect for the garage itself: the main breaker in the subpanel satisfies that requirement as long as it's positioned correctly.

Grounding Requirements for Detached Structures

Article 250 of the NEC requires detached structures supplied by feeders to have their own grounding electrode system. This means several important things for your installation:

First, we must run a four-wire feeder with separate neutral and equipment grounding conductors. In the garage subpanel, neutrals and grounds must remain isolated: they cannot be bonded together like they are in your home's main panel.

Second, the garage needs its own grounding electrodes. These are typically ground rods driven into the earth near the garage and properly bonded to the subpanel. This grounding system is critical for safety and is closely inspected during the approval process.

Underground Wiring Considerations

Many detached garages require underground feeder installation. When that's the case, Article 300 governs burial depth, conduit requirements, and physical protection. All feeder conductors must be installed together in the same conduit system, and minimum cover requirements must be met.

In Aldie and South Riding, where many homes have detached garages, underground runs are common. While this work isn't visible once complete, it's a major component that inspectors review carefully.

The depth requirements vary depending on the type of wiring method used, but typically range from 18 to 24 inches for residential installations. Proper warning tape and conduit protection are also required to prevent future damage from digging or landscaping.

Disconnect and Safety Requirements

Homeowners often ask whether they need a large shutoff switch mounted outside their garage. Usually, the answer is no. Article 225 requires a disconnecting means for detached buildings, but it can be located inside the building as long as it's immediately nearest the point where the feeder enters.

In most residential installations, the main breaker in the garage subpanel satisfies this requirement. As long as that panel is positioned right where the feeder enters the structure, no separate exterior disconnect is needed.

For the EV charger itself, Article 625 only requires a separate disconnect when the equipment exceeds certain ratings. Most residential chargers don't meet those thresholds, which means the circuit breaker supplying the charger serves as the required disconnecting means.

Protection and Safety Features

Ground-fault protection requirements can vary depending on your charger type and installation method. Receptacle-based EV chargers may require GFCI protection under Articles 210 and 625, while hardwired chargers often rely on internal protection built into the equipment.

Manufacturer installation instructions, which are enforceable under Article 110, must always be followed. Local inspection authorities in Gainesville and Haymarket may have additional interpretations that affect the final design.

Permits and Inspections

Installing an EV charger in a detached garage almost always requires an electrical permit. That permit ensures the load calculation has been properly reviewed, the feeder and grounding are correct, and the installation meets current safety standards.

The inspection process covers several key areas: feeder sizing and installation, subpanel location and connections, grounding electrode installation, EV charger circuit installation, and overall code compliance. Having experienced professionals handle this process ensures smooth approvals and avoids costly delays.

What This Means for Your Project

From the outside, an EV charger looks like a simple wall-mounted device. Behind the scenes, a proper detached garage installation often involves upgrading how the garage receives power, installing a subpanel, adding grounding electrodes, running underground wiring, and ensuring compliance with multiple NEC articles.

None of this complexity exists to make the job harder or more expensive. It exists to ensure the installation is safe, reliable, and built to handle modern electrical demands. When done correctly, you get a code-compliant setup that works properly for decades.

If your detached garage currently has only one small branch circuit, installing an EV charger isn't just about mounting equipment on the wall. It's an infrastructure upgrade that brings your garage's electrical system up to modern standards.

Getting Started with Your Installation

Every detached garage situation is unique. The distance from your main panel, existing electrical capacity, underground obstacles, and local code interpretations all affect what your specific installation will involve.

If you're considering an EV charger installation in Sterling or Chantilly, the best first step is having your existing electrical system evaluated by experienced professionals. We can assess your current garage wiring, determine what upgrades are needed, and provide clear information about the scope and cost before any work begins.

At Auto Charge Pros, we handle detached garage EV charger installations regularly throughout Northern Virginia. We understand the code requirements, manage the permit process, and complete installations that pass inspection the first time. If you'd like to understand what your specific installation would involve, contact us for a detailed evaluation of your property.