.solar-wire-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 700px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 10px;
background-color: #fdfdfd;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}
.solar-wire-calculator-container h2 {
color: #2c3e50;
text-align: center;
margin-bottom: 25px;
font-size: 1.8em;
border-bottom: 2px solid #4CAF50;
padding-bottom: 10px;
}
.solar-wire-calculator-container .input-group {
margin-bottom: 18px;
display: flex;
flex-direction: column;
}
.solar-wire-calculator-container label {
display: block;
margin-bottom: 8px;
color: #34495e;
font-weight: bold;
font-size: 0.95em;
}
.solar-wire-calculator-container input[type="number"],
.solar-wire-calculator-container select {
width: calc(100% – 22px);
padding: 12px;
border: 1px solid #ccc;
border-radius: 6px;
font-size: 1em;
box-sizing: border-box;
transition: border-color 0.3s ease;
}
.solar-wire-calculator-container input[type="number"]:focus,
.solar-wire-calculator-container select:focus {
border-color: #4CAF50;
outline: none;
box-shadow: 0 0 5px rgba(76, 175, 80, 0.5);
}
.solar-wire-calculator-container button {
background-color: #4CAF50;
color: white;
padding: 14px 25px;
border: none;
border-radius: 6px;
cursor: pointer;
font-size: 1.1em;
font-weight: bold;
width: 100%;
transition: background-color 0.3s ease, transform 0.2s ease;
margin-top: 20px;
}
.solar-wire-calculator-container button:hover {
background-color: #45a049;
transform: translateY(-2px);
}
.solar-wire-calculator-container .result {
margin-top: 30px;
padding: 20px;
border: 1px solid #d4edda;
background-color: #e6ffe6;
border-radius: 8px;
font-size: 1.1em;
color: #155724;
line-height: 1.6;
}
.solar-wire-calculator-container .result p {
margin: 0 0 10px 0;
}
.solar-wire-calculator-container .result p:last-child {
margin-bottom: 0;
}
.solar-wire-calculator-container .result strong {
color: #2c3e50;
}
.solar-wire-calculator-container .error {
color: #d8000c;
background-color: #ffbaba;
border: 1px solid #d8000c;
padding: 10px;
border-radius: 5px;
margin-top: 15px;
text-align: center;
}
.solar-wire-calculator-container .info-text {
font-size: 0.85em;
color: #666;
margin-top: -10px;
margin-bottom: 15px;
padding-left: 5px;
}
Solar Panel Wire Size Calculator
Typical DC system voltages are 12V, 24V, or 48V.
Sum of the maximum power (Pmax) of all panels in your array.
Distance from panels to charge controller/inverter.
Recommended is 1-3% for DC circuits.
Copper
Aluminum
function calculateWireSize() {
var systemVoltage = parseFloat(document.getElementById("systemVoltage").value);
var totalPanelWattage = parseFloat(document.getElementById("totalPanelWattage").value);
var oneWayDistance = parseFloat(document.getElementById("oneWayDistance").value);
var desiredVoltageDrop = parseFloat(document.getElementById("desiredVoltageDrop").value);
var wireMaterial = document.getElementById("wireMaterial").value;
var resultDiv = document.getElementById("result");
resultDiv.style.display = 'none';
resultDiv.innerHTML = ";
// Input validation
if (isNaN(systemVoltage) || systemVoltage <= 0 ||
isNaN(totalPanelWattage) || totalPanelWattage <= 0 ||
isNaN(oneWayDistance) || oneWayDistance <= 0 ||
isNaN(desiredVoltageDrop) || desiredVoltageDrop 100) {
resultDiv.style.display = 'block';
resultDiv.className = 'result error';
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Resistivity constant (K) for Circular Mils formula at 20°C
// K = Ohms per circular mil-foot
var K;
if (wireMaterial === "copper") {
K = 10.4; // Copper
} else {
K = 17.0; // Aluminum
}
// Calculate Maximum System Current (I)
// NEC requires multiplying the maximum current by 1.25 for continuous loads.
// For solar, this is typically the Imp (current at max power) or Isc (short circuit current)
// For simplicity, we'll use Pmax/Vsys * 1.25
var maxCurrent = (totalPanelWattage / systemVoltage) * 1.25; // Amperes
// Calculate Allowable Voltage Drop in Volts (Vd)
var allowableVoltageDropVolts = (desiredVoltageDrop / 100) * systemVoltage;
// Ensure minimum voltage drop to avoid division by zero or extremely large wire sizes for 0% drop
if (allowableVoltageDropVolts < 0.01) { // Set a practical minimum
allowableVoltageDropVolts = 0.01;
}
// Calculate Minimum Required Circular Mils (CM)
// Formula: CM = (2 * K * I * L) / Vd
// 2 * L because it's a two-way circuit (out and back)
var requiredCircularMils = (2 * K * maxCurrent * oneWayDistance) / allowableVoltageDropVolts;
// AWG/kcmil lookup table (Circular Mils values)
// Sorted from smallest CM (largest AWG number) to largest CM (smallest AWG number/kcmil)
var awgSizes = [
{ awg: "18 AWG", cm: 1624 },
{ awg: "16 AWG", cm: 2582 },
{ awg: "14 AWG", cm: 4107 },
{ awg: "12 AWG", cm: 6530 },
{ awg: "10 AWG", cm: 10380 },
{ awg: "8 AWG", cm: 16510 },
{ awg: "6 AWG", cm: 26240 },
{ awg: "4 AWG", cm: 41740 },
{ awg: "2 AWG", cm: 66360 },
{ awg: "1 AWG", cm: 83690 },
{ awg: "1/0 AWG", cm: 105600 },
{ awg: "2/0 AWG", cm: 133100 },
{ awg: "3/0 AWG", cm: 167800 },
{ awg: "4/0 AWG", cm: 211600 },
{ awg: "250 kcmil", cm: 250000 },
{ awg: "300 kcmil", cm: 300000 },
{ awg: "350 kcmil", cm: 350000 },
{ awg: "400 kcmil", cm: 400000 },
{ awg: "500 kcmil", cm: 500000 },
{ awg: "600 kcmil", cm: 600000 },
{ awg: "700 kcmil", cm: 700000 },
{ awg: "750 kcmil", cm: 750000 },
{ awg: "800 kcmil", cm: 800000 },
{ awg: "900 kcmil", cm: 900000 },
{ awg: "1000 kcmil", cm: 1000000 }
];
var recommendedAWG = "N/A";
var selectedCM = 0;
for (var i = 0; i = requiredCircularMils) {
recommendedAWG = awgSizes[i].awg;
selectedCM = awgSizes[i].cm;
break;
}
}
if (recommendedAWG === "N/A") {
recommendedAWG = "Larger than 1000 kcmil (consult an electrician)";
selectedCM = awgSizes[awgSizes.length – 1].cm; // Use the largest available for calculation
}
// Calculate actual voltage drop with the selected wire size
// Vd = (2 * K * I * L) / CM
var actualVoltageDropVolts = (2 * K * maxCurrent * oneWayDistance) / selectedCM;
var actualVoltageDropPercent = (actualVoltageDropVolts / systemVoltage) * 100;
resultDiv.className = 'result';
resultDiv.innerHTML =
"Calculated Maximum Current: " + maxCurrent.toFixed(2) + " A" +
"Minimum Required Circular Mils: " + requiredCircularMils.toFixed(2) + " CM" +
"Recommended Wire Size: " + recommendedAWG + "" +
"Actual Voltage Drop: " + actualVoltageDropVolts.toFixed(2) + " V" +
"Actual Voltage Drop Percentage: " + actualVoltageDropPercent.toFixed(2) + " %" +
"Note: This calculation is based on voltage drop. Always verify with local electrical codes for ampacity and other safety requirements.";
resultDiv.style.display = 'block';
}
Copper has lower resistance than aluminum.
Understanding Solar Panel Wire Sizing
Proper wire sizing is a critical, yet often overlooked, aspect of designing a safe and efficient solar power system. Using wires that are too small for your system's current and distance can lead to significant energy losses, reduced performance, and even fire hazards. This calculator helps you determine the appropriate wire size for your DC solar circuits based on voltage drop considerations.
Why Wire Sizing Matters: Voltage Drop
When electricity flows through a wire, it encounters resistance, which causes a drop in voltage. This phenomenon is known as "voltage drop." In a solar system, excessive voltage drop means:
- Reduced Efficiency: Less power reaches your batteries or inverter, meaning your panels aren't performing at their full potential.
- Slower Charging: Batteries will take longer to charge, or may not fully charge.
- Component Damage: Some electronics are sensitive to voltage fluctuations and can be damaged by consistently low voltage.
- Heat Generation: Resistance also generates heat. Undersized wires can overheat, posing a fire risk.
The National Electrical Code (NEC) generally recommends keeping voltage drop below 3% for power circuits to ensure optimal performance and safety. For critical DC solar circuits, many designers aim for 1-2%.
Key Factors in Wire Sizing
The calculator takes into account several crucial factors:
- System Voltage (V): Higher voltage systems (e.g., 48V) draw less current for the same amount of power compared to lower voltage systems (e.g., 12V). Lower current means less voltage drop, allowing for smaller wires or longer distances.
- Total Panel Wattage (W): This determines the total power your system can generate. The calculator uses this along with system voltage to estimate the maximum current your wires will carry.
- One-Way Distance (ft): The longer the wire run from your solar panels to your charge controller or inverter, the greater the resistance and thus the greater the voltage drop.
- Desired Voltage Drop (%): This is your target maximum allowable voltage drop. A lower percentage requires a larger wire size.
- Wire Material: Copper is a better conductor than aluminum, meaning it has lower resistance for the same wire size. While aluminum is lighter and cheaper for very large gauges, copper is generally preferred for solar DC wiring due to its superior conductivity and corrosion resistance.
How the Calculator Works
This calculator uses the standard voltage drop formula to determine the minimum required wire cross-sectional area in Circular Mils (CM). It then matches this CM value to the closest standard American Wire Gauge (AWG) or kcmil size. It also applies a 1.25x safety factor to the maximum current, as required by the NEC for continuous loads like solar PV circuits, ensuring the wire can safely handle sustained operation.
Important Considerations
- Ampacity: While this calculator focuses on voltage drop, wire sizing also involves considering the wire's ampacity (the maximum current it can safely carry without overheating). Always ensure your chosen wire size meets both voltage drop requirements and local electrical code ampacity requirements for your specific installation environment (e.g., temperature, conduit fill).
- Overcurrent Protection: Wires must be protected by appropriately sized fuses or circuit breakers to prevent damage from overcurrents.
- Professional Advice: This calculator provides an estimate for planning purposes. For complex or grid-tied systems, always consult with a qualified electrician or solar professional to ensure compliance with all local codes and safety standards.