What wire size do I need for a 48V, 3000W inverter?

A 3,000W inverter at 48V draws 62.5A. For a 3-foot run with 1% max voltage drop: 4 AWG (21mm²) is sufficient. For a 12V, 1,500W inverter drawing 125A, you'd need 3/0 AWG — which is why 48V systems are vastly easier to wire.

Why is 48V better than 12V for off-grid wiring?

For the same power, a 48V system carries 4× less current than a 12V system. Lower current means much thinner (cheaper) wire, less heat, and smaller voltage drops over the same distance. A 1,200W load at 12V needs 100A and requires 2/0 AWG for a 10-foot run — at 48V, it draws only 25A and 8 AWG is sufficient.

DC Wire Size Calculator

Size DC wiring for 12V, 24V, and 48V solar and battery systems — get both AWG and mm² with voltage drop analysis.

DC circuit parameters

Current?

One-way distance?

DC voltage?

Max voltage drop?

Recommended DC wire size

4/0 AWG

Metric equivalent107.2 mm²

Actual voltage drop0.029V (0.06%)

Power loss0.9W

Efficiency loss0.06%

Next size up: 3/0 AWG (85.0 mm²) reduces voltage drop to 0.08% — consider for permanent installations.

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How to Use This Calculator

DC wire sizing differs from AC

DC wire sizing is more demanding than AC for the same power level because DC systems typically operate at lower voltages. At 12V, transferring 1,200W requires 100A — requiring extremely large conductors for any meaningful run length. At 48V, the same 1,200W only needs 25A, making wiring far more practical. This calculator is optimized for DC circuits: 12V, 24V, 48V solar and battery systems.

Enter current, distance, and voltage

Input the maximum continuous DC current in amps, the one-way distance in feet, and select your DC system voltage. For battery-to-inverter cables, use the inverter's rated input amps. For solar runs, use panel Isc × 1.25.

Compare AWG and mm² results

The result shows both AWG (American standard) and mm² (metric/IEC) for easy cross-referencing when sourcing wire from different suppliers. The "next size up" suggestion shows the efficiency gain from buying slightly heavier wire — often worth $20–40 extra for the life of the system.

The Formula

Total circuit length = one-way distance × 2 (round trip in feet) Allowed voltage drop = DC voltage × drop% / 100 Max resistance = (allowed drop × 1000) / (total ft × amps) [Ω/1000ft] Select thinnest AWG where: Resistance ≤ max resistance Ampacity ≥ load current Actual drop = (total ft × wire resistance × amps) / 1000 Power loss = actual drop voltage × amps Efficiency loss = power loss / (voltage × amps) × 100

The key insight for DC design: at 12V, a mere 2% voltage drop is only 0.24V — requiring extremely low-resistance (thick) wire even for modest current over short distances. At 48V, a 2% drop is 0.96V — 4× more headroom, allowing much thinner wire. This is the strongest argument for designing off-grid systems at 48V whenever possible.

Example

Battery bank to inverter — 3 feet, 48V, 3,000W

A 3,000W inverter at 48V draws 3,000/48 = 62.5A. The battery bank is 3 feet from the inverter. Maximum 1% voltage drop.

Current62.5A

Round trip3ft × 2 = 6ft

Allowed drop (1%)48V × 1% = 0.48V

Max resistance0.48 × 1000 / (6 × 62.5) = 1.28 Ω/kft

Result

Recommended wire4 AWG (0.2485 Ω/kft)

Actual drop6 × 0.2485 × 62.5 / 1000 = 0.093V (0.19%)

Power loss0.093V × 62.5A = 5.8W

Even on this short 3-foot run, a 4 AWG conductor comfortably handles the 62.5A load. If this were a 12V/1,500W inverter instead (125A!), you'd need 2/0 AWG for the same 3-foot run at 1% drop — illustrating why 48V systems are dramatically easier to wire.

FAQ

Why are battery-to-inverter cables so large? ▼

Because of Ohm's law at low voltage: P = V × I, so I = P / V. A 3,000W inverter at 12V draws 250A — a current level that requires 3/0 AWG or larger for even a few feet of run. At 48V, the same inverter draws only 62.5A, manageable with 4 AWG. The battery-to-inverter cables are always the largest cables in the system, and they must be kept as short as possible — both to minimize resistance and because the very high short-circuit currents possible from a large battery bank make this the most dangerous circuit in the system.

Should I use flexible welding cable or rigid building wire for battery connections? ▼

For battery interconnects and short, high-current runs, flexible welding cable (typically rated at 600V DC) is much easier to work with than rigid THHN building wire. It bends easily around battery terminals, is available in red and black for polarity identification, and handles vibration well in mobile installations (RV, marine, van). For runs in conduit or fixed installations, THHN is fine. The electrical characteristics are essentially identical — the choice is purely practical. Use copper lugs appropriate for the wire gauge and terminal type.

What is the maximum DC voltage I can use without special wiring? ▼

For residential off-grid systems, 48V is the practical maximum for standard wiring and components. Above 48V DC starts requiring high-voltage DC safety precautions. Solar PV string voltages (typically 150–600V DC for MPPT inputs) require PV-rated wire and conduit for the exposed wiring between panels and inverter, but the battery bank itself stays at 48V. Utility-scale and commercial systems use higher DC voltages (600V–1500V) with appropriate equipment ratings and safety protocols.