Solar Cable & Wire Size Calculator

Pick DC or AC cable cross-section with built-in voltage drop check and AWG equivalent.

Cable Type

Current

1 A20 A200 A

One-way Length

1 m10 m100 m

System Voltage

Allowable Voltage Drop

1%3%10%

Recommended cable

Recommended Cross-Section

6 mm²

AWG 8

Actual Voltage Drop

2.39%

1.15 V

Required (Raw)

4.78 mm²

Before IEC rounding

Copper Cost

₹480

up to ₹840

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How to size solar cable

Step-by-step guide to picking the right copper cross-section for DC and AC solar circuits.

Identify your circuit
Panel-to-charge controller (DC), inverter-to-distribution-board (AC 1φ), or grid-tie export cable (AC 1φ or 3φ).
Measure one-way length
Use a string or measuring tape. Don't guess — cable cost scales linearly.
Find max current
For DC: string Isc × 1.25. For AC: inverter continuous rating in amps (kVA × 1000 / V).
Choose allowable drop
3% for DC, 2% for AC branches, 1% for long cable runs.
Read recommended mm²
The calculator rounds up to the next standard IEC size. Don't downsize below this.
Buy double-insulated solar cable
TUV-certified, UV-resistant, rated for at least 1000V DC (or 600V AC).

Why cable sizing matters

Under-sized cable is the most common silent energy loss in residential solar. A 3% voltage drop means 3% less energy reaches your inverter and 3% less income from net metering — every day, for 25 years. On a 5 kW system, that's roughly 200 kWh/year or ₹1,500 lost annually. The one-time cost of the correct cable pays back in under a year.

Standard IEC cross-sections for solar

mm²	AWG	Max Current (DC)	Typical Use
2.5	14	25 A	Panel to combiner
4	12	32 A	Short string runs
6	10	41 A	Medium string runs
10	8	57 A	Combiner to inverter
16	6	76 A	Long runs / 10kW systems

Pair this with the Inverter Size Calculator to confirm the AC output current your cable must handle, and the Panel Azimuth Calculator when finalising your array layout and DC cable runs.

Frequently Asked Questions

What cable size do I need for a solar system?

Cable size depends on current (A), cable length (m), system voltage (V), and allowable voltage drop (%). For a typical 5 kW rooftop DC run of 15m at 48V, you'd need 6-10 mm² copper. Our calculator computes the minimum cross-section that keeps drop under your target (3% DC, 2% AC).

What is the formula for solar cable sizing?

Voltage drop V = (2 × L × I × ρ) / A, where L = one-way length in meters, I = current in amps, ρ = copper resistivity (0.0172 Ω·mm²/m), A = cross-section in mm². Rearrange to solve for A when V is your allowable drop.

Why is 3% voltage drop the standard for DC solar?

Above 3% drop, you lose efficiency and reduce charging headroom. Most design codes (NEC, IEC, IS 15150) recommend ≤3% for DC solar arrays and ≤2% for AC branch circuits to the main panel. Lower drop = slightly higher copper cost but measurably better system performance.

Should I use copper or aluminum solar cable?

Copper for residential solar — lower resistance, corrosion resistant, available in fine strands for flexibility. Aluminum is cheaper and used in utility-scale runs above 50 mm², but requires specific connectors and is not recommended for rooftop residential installations.

What gauge is 4mm² solar cable in AWG?

4 mm² ≈ AWG 12 (American Wire Gauge). Common solar conversions: 2.5mm² ≈ AWG 14, 4mm² ≈ AWG 12, 6mm² ≈ AWG 10, 10mm² ≈ AWG 8, 16mm² ≈ AWG 6.

Do I need different cable types for DC and AC?

Yes. DC solar cable is UV-stabilized, double-insulated, rated for 1000-1500V DC with red/black identifiers. AC cable to your main panel is standard house wiring (single-phase 230V or three-phase 415V). Using AC cable for DC strings causes UV degradation and insulation failure within 2-3 years.

What happens if cable is undersized?

Three problems: (1) voltage drop reduces panel output — every 1% drop = 1% less energy harvested, (2) cable overheats, potentially melting insulation and starting a fire, (3) circuit breaker tripping.