EV Charger for Detached Garages: Conduit Guide

Detached garages are common across Aiken, SC. Whether it is a traditional two-car garage set back from the house, a converted barn, or a workshop building, many homeowners park their electric vehicles in structures that are physically separated from their main electrical panel. Installing an EV charger in these locations is absolutely doable, but it involves more than just mounting a charger on the wall.

The primary challenge is getting electrical power from your home's panel to the detached structure. This almost always means running wire underground through conduit, and that process involves trenching, proper conduit selection, correct wire sizing, and permitting. Here is exactly what is involved so you can plan and budget accurately.

Why Underground Conduit Is Necessary

You cannot simply run an extension cord or surface-mounted wire from your house to a detached garage. The National Electrical Code requires that any electrical wiring running between separate structures be properly protected. For most residential installations, this means underground conduit.

Overhead runs between structures are sometimes possible, but they come with strict requirements for minimum clearance heights (typically 10 to 15 feet depending on the area below), and most homeowners find them visually undesirable. For EV charger circuits that carry 40 to 60 amps of continuous load, underground conduit is the standard approach and the one we recommend for virtually every detached garage installation in Aiken.

Underground conduit protects the wire from physical damage, moisture, rodents, and UV exposure. It also keeps the installation neat and invisible once the trench is backfilled and the landscaping is restored.

Burial Depth Requirements

The National Electrical Code specifies minimum burial depths based on the type of conduit used. These are minimums - going deeper is always acceptable and sometimes preferable.

PVC conduit (Schedule 80): Minimum 18 inches of cover. This is the most common conduit type for residential underground runs. Schedule 80 PVC is thick-walled, gray in color, and rated for direct burial. Schedule 40 PVC (the white, thinner-walled type used for drain plumbing) is also acceptable in many jurisdictions at 18 inches, but we prefer Schedule 80 for its superior impact resistance.

Rigid metal conduit (RMC): Minimum 6 inches of cover. RMC is the strongest conduit option but is more expensive and harder to work with. It is rarely used for residential underground runs unless the trench needs to be shallow due to existing utilities or hardscape.

Direct burial cable (UF): Minimum 24 inches of cover. This is wire rated for direct contact with soil, without conduit protection. While code-compliant, we do not use direct burial cable for EV charger circuits. The wire cannot be replaced or upgraded without re-trenching, and it is more vulnerable to damage from future digging. Always use conduit.

In Aiken County, we typically trench to 24 inches regardless of conduit type. This provides a safety margin above the 18-inch minimum and keeps the conduit well below the depth of typical landscaping activities, irrigation system installations, and shallow utility runs.

Conduit Type and Sizing

For an EV charger circuit, we typically use 1-inch or 1.25-inch Schedule 80 PVC conduit for the underground run. The conduit must be large enough to accommodate the number and size of wires being pulled through it, with the NEC limiting conduit fill to 40% of the internal cross-sectional area when pulling three or more conductors.

A typical EV charger installation requires four conductors: two hot wires, one neutral, and one ground. For a 60-amp circuit using 6 AWG copper wire, 1-inch conduit provides adequate space. If we anticipate future needs, such as adding circuits for lighting or outlets in the detached garage, we will upsize to 1.25-inch or even 1.5-inch conduit. The conduit itself is inexpensive, and upsizing during trenching adds minimal cost compared to re-trenching later.

At each end of the underground run, the conduit transitions from underground to above-ground. This is done with a 90-degree sweep (a large-radius elbow) that brings the conduit up through the foundation or wall and into the structure. We use an LB fitting or a weather head at the transition point to prevent water from entering the conduit.

Wire Sizing for the Distance

This is where detached garage installations differ significantly from attached garage installations. Wire has electrical resistance, and that resistance increases with length. Over long runs, this resistance causes voltage drop, meaning the voltage at the charger end is lower than the voltage at the panel end.

The NEC recommends keeping voltage drop below 3% for branch circuits and 5% total from the service entrance to the farthest outlet. For a 240-volt circuit, 3% voltage drop means no more than 7.2 volts lost over the run. At 48 amps of continuous load, 6 AWG copper wire can only run about 65 feet before exceeding 3% voltage drop.

If your detached garage is 80 feet from your panel, you may need to upsize to 4 AWG wire. At 120 feet, you might need 3 AWG or even 2 AWG. Each wire gauge increase adds material cost, but it is essential for the charger to operate at full speed and for the circuit to operate safely.

Here is a practical reference for a 48-amp EV charger circuit at 240 volts with 3% maximum voltage drop:

Up to 65 feet: 6 AWG copper (standard for most attached garage installations)
65 to 100 feet: 4 AWG copper
100 to 150 feet: 3 AWG copper
150 to 200 feet: 2 AWG copper

We calculate voltage drop for every detached garage installation based on the actual measured distance, the charger's amperage rating, and the circuit voltage. There is no guesswork involved.

The Trenching Process

Trenching is often the most disruptive part of a detached garage EV charger installation, but with proper planning, the impact is manageable.

Before any digging begins, we call 811 to have underground utilities marked. This is not optional - it is legally required and critical for safety. Gas lines, water lines, sewer lines, cable TV, phone lines, and irrigation systems can all be in the path of your trench. The utility marking process takes a few business days, so we schedule this before the installation date.

Route planning is the next step. We select the shortest practical path between your main panel and the detached garage while avoiding trees, patios, driveways, and known utility locations. Sometimes the shortest path crosses a concrete driveway, which would require saw-cutting and patching. In those cases, routing around the driveway is usually more cost-effective even though the trench is longer.

Trenching methods depend on the soil conditions and the distance involved. For short runs through open yard, we dig by hand. For longer runs, a trenching machine or mini-excavator makes the work faster and more consistent. The trench is typically 6 to 8 inches wide and 24 inches deep.

Conduit installation happens once the trench is dug to the correct depth. We lay the conduit in the trench, glue all joints with PVC cement, and verify that the conduit is properly supported and free of kinks. A pull rope or fish tape is fed through the conduit before burial to facilitate wire pulling later.

Backfilling is done in layers. We add a few inches of fill, compact it, and repeat until the trench is level with the surrounding grade. If the trench crosses a lawn, we tamp the soil carefully to prevent settling that would leave a visible depression. Most lawns recover naturally within a few weeks as the grass fills in.

Permitting in Aiken County

Electrical work in Aiken County requires a permit for new circuit installations, and a detached garage EV charger circuit absolutely qualifies. The permitting process involves submitting an application, paying a fee, and scheduling an inspection after the work is complete.

Unity Power & Light handles the entire permitting process for you. We submit the application, pay the fee (included in our quote), and coordinate the inspection. The inspector verifies that the installation meets NEC requirements for burial depth, conduit type, wire sizing, grounding, and charger installation. Once passed, you receive a signed-off permit for your records.

We strongly advise against skipping the permit. Unpermitted electrical work can create problems when you sell your home, file an insurance claim, or have a future inspection. The permit cost is a small fraction of the total installation cost and provides documentation that the work was done correctly.

Cost Factors for Detached Garage Installations

A detached garage EV charger installation costs more than an attached garage installation due to the additional materials and labor involved in trenching and underground conduit. Here are the primary factors that influence the total cost.

Distance between panel and garage: This is the single biggest cost driver. Every additional foot of trench adds conduit, wire, and labor. A 30-foot run is substantially less expensive than a 100-foot run.

Obstacles in the path: Crossing a concrete driveway, navigating around a pool, or weaving between mature tree roots adds complexity and cost. Open yard with no obstacles is the most economical scenario.

Wire gauge required: Longer runs require heavier wire to compensate for voltage drop. 2 AWG copper costs roughly three times as much per foot as 6 AWG copper.

Panel capacity: If your existing panel cannot accommodate a 60-amp breaker for the EV charger, a panel upgrade adds to the total project cost. This is the same consideration for any EV charger installation, not specific to detached garages.

Landscaping restoration: We backfill and compact the trench, but if the trench crosses premium landscaping, pavers, or other finished surfaces, restoration costs may apply.

Subpanel option: For detached garages that need multiple circuits (EV charger, lighting, outlets, workshop equipment), installing a subpanel in the garage can be more economical than running multiple individual circuits. A single large feeder cable supplies the subpanel, and individual circuits branch out from there.

Alternative Approaches

While underground conduit is the standard approach, a few alternatives exist for specific situations.

Existing conduit or wire path: Some detached garages already have electrical service, run from the main panel at some point in the past. If the existing wire run has spare capacity or the conduit is large enough to pull additional wire, we may be able to add an EV charger circuit without new trenching. We assess this during our site visit.

Subpanel upgrade: If the detached garage has a small subpanel (say 60 amps) that is underutilized, we may be able to add an EV charger circuit from the existing subpanel without running new wire from the house. This depends entirely on the existing wiring capacity and the loads already served by the subpanel.

Charging at the house instead: Some homeowners decide that the cost of running power to a detached garage is not justified, especially if they can park near the house occasionally. Installing the charger on an exterior wall of the house near the driveway, with a long charging cable that reaches the parking area, can be a practical compromise. Most EV chargers come with 18 to 25 feet of cable.

Portable Level 2 chargers: A 240V outlet can be installed at either location, and a portable Level 2 charger can be moved between them. This is less convenient than a permanent installation but avoids the cost of a second charger.

What to Expect from the Installation Process

A typical detached garage EV charger installation takes one to two days. Here is the general timeline.

Day 1: Trenching, conduit installation, and wire pulling. We dig the trench, lay and glue the conduit, pull the wire, and begin backfilling. If the run is short and conditions are favorable, we may complete the electrical connections on the same day.

Day 2: Electrical connections and charger installation. We connect the circuit at the panel, install the breaker, mount and wire the charger in the garage, and test the complete system. We verify voltage at the charger, test GFCI operation, and demonstrate the charger to you.

After the installation, we schedule the electrical inspection. The inspector typically visits within a few business days. If any adjustments are needed (which is rare with professional installation), we address them promptly at no additional cost.

Related Services

Learn more about our Outdoor & Detached Garage EV Charger Installation and Underground Wiring services.

EV Charger for Detached Garages: What Underground Conduit Actually Involves