Wire Sizing Charts
Correct wire sizing is critical for safety and performance. Undersized wires cause voltage drop (lost power) and overheating (fire risk). Use these charts to select the right wire for every connection in your solar system.
The 2% voltage drop rule
Total voltage drop across any wire run should be under 2% of your system voltage. For a 12V system, that means less than 0.24V drop. For 48V, less than 0.96V. Longer wire runs and higher currents require thicker wire. All charts below are sized for 2% maximum drop.
Solar Panel to Charge Controller (PV Wire)
Use solar-rated PV wire (UV resistant, rated for outdoor use). Never use regular THHN for outdoor panel connections. Distance is one-way cable length from panels to controller.
| Current | 5m | 10m | 15m | 20m |
|---|---|---|---|---|
| 10A | 4mm2 (12 AWG) | 4mm2 (12 AWG) | 6mm2 (10 AWG) | 6mm2 (10 AWG) |
| 15A | 4mm2 (12 AWG) | 6mm2 (10 AWG) | 6mm2 (10 AWG) | 10mm2 (8 AWG) |
| 20A | 4mm2 (12 AWG) | 6mm2 (10 AWG) | 10mm2 (8 AWG) | 10mm2 (8 AWG) |
| 30A | 6mm2 (10 AWG) | 10mm2 (8 AWG) | 10mm2 (8 AWG) | 16mm2 (6 AWG) |
| 40A | 10mm2 (8 AWG) | 10mm2 (8 AWG) | 16mm2 (6 AWG) | 16mm2 (6 AWG) |
| 50A | 10mm2 (8 AWG) | 16mm2 (6 AWG) | 16mm2 (6 AWG) | 25mm2 (4 AWG) |
| 60A | 10mm2 (8 AWG) | 16mm2 (6 AWG) | 25mm2 (4 AWG) | 25mm2 (4 AWG) |
Battery to Inverter Cable
Battery cables carry the highest current in your system. Keep cables as short as possible (under 1.5m). Use flexible copper cable with proper lugs. Always include a fuse or breaker between battery and inverter.
| System / Inverter | Max Amps | Cable Size | Fuse/Breaker |
|---|---|---|---|
| 12V / 500W | ~42A | 10mm2 (8 AWG) | 50A |
| 12V / 1,000W | ~83A | 25mm2 (4 AWG) | 100A |
| 12V / 2,000W | ~167A | 50mm2 (1/0 AWG) | 200A |
| 24V / 1,000W | ~42A | 10mm2 (8 AWG) | 50A |
| 24V / 2,000W | ~83A | 25mm2 (4 AWG) | 100A |
| 24V / 3,000W | ~125A | 35mm2 (2 AWG) | 150A |
| 24V / 5,000W | ~208A | 70mm2 (2/0 AWG) | 250A |
| 48V / 3,000W | ~63A | 16mm2 (6 AWG) | 80A |
| 48V / 5,000W | ~104A | 25mm2 (4 AWG) | 125A |
| 48V / 8,000W | ~167A | 50mm2 (1/0 AWG) | 200A |
Inverter to Load Panel (AC Wiring)
Use THHN wire for AC connections from inverter to breaker panel and outlets. Follow the Philippine Electrical Code (PEC) for indoor wiring.
| Total Load | Wire Size | Breaker |
|---|---|---|
| Up to 1,000W | 2.0mm2 THHN (14 AWG) | 15A |
| 1,000-2,000W | 3.5mm2 THHN (12 AWG) | 20A |
| 2,000-3,000W | 5.5mm2 THHN (10 AWG) | 30A |
| 3,000-5,000W | 8.0mm2 THHN (8 AWG) | 40A |
| 5,000-8,000W | 14mm2 THHN (6 AWG) | 50A |
Wire buying tips for the Philippines
- PV wire — Buy from solar suppliers or AliExpress. Look for "TUV certified" or "PV1-F" rated wire. Available in 4mm2, 6mm2, and 10mm2.
- Battery cables — Sold by the meter at electrical supply stores. Ask for "welding cable" or "flexible copper cable" in the right size. Buy proper copper lugs and a crimping tool.
- THHN wire — Available at any hardware store (Ace, Handyman, True Value, CDR King). Sold in 75m or 150m rolls. Brands: Phelps Dodge, PDI, Boston.
- MC4 connectors — Always use proper MC4 crimp connectors with a crimping tool. Never solder MC4 connections. Loose MC4 connections are a leading cause of solar fires.
- Grounding — Use 8mm2 (8 AWG) solid copper wire for grounding. Connect panel frames, mounting rails, and inverter chassis to a ground rod.
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