This calculator estimates the annual energy output of a solar photovoltaic (PV) system. Understanding this output is crucial for homeowners and businesses considering solar installations, helping to gauge potential savings and the system's effectiveness. The calculation is based on several key factors:
Panel Wattage: The rated power output of a single solar panel under Standard Test Conditions (STC).
Number of Panels: The total quantity of solar panels installed in the system.
Peak Sun Hours: The average number of hours per day when solar irradiance averages 1000 W/m², equivalent to full sun. This varies significantly by geographic location and weather patterns.
System Losses: Energy lost due to various factors like inverter efficiency, wiring resistance, temperature effects, shading, and dirt accumulation. Expressed as a percentage.
Operational Days per Year: The number of days the system is expected to generate power, typically accounting for maintenance or seasonal variations.
The Calculation Logic
The formula used by this calculator is as follows:
Total System Wattage = Panel Wattage (W) * Number of Panels
Energy Production per Day (Wh) = Total System Wattage * Average Peak Sun Hours * (1 - (System Losses % / 100))
Estimated Annual Energy Production (Wh) = Energy Production per Day (Wh) * Operational Days per Year
The final output is presented in Watt-hours (Wh) per year, which can then be converted to kilowatt-hours (kWh) by dividing by 1000 for easier comparison with electricity bills.
Factors Influencing Real-World Output
While this calculator provides a good estimate, actual energy production can vary due to:
Geographic Location: Affects the intensity and duration of sunlight.
Panel Orientation and Tilt: The angle and direction panels face significantly impact sunlight absorption.
Shading: Obstructions like trees or buildings can drastically reduce output.
Weather Conditions: Cloud cover, rain, and snow reduce sunlight reaching the panels.
Temperature: Solar panels are generally less efficient at higher temperatures.
Panel Degradation: Solar panels slowly lose efficiency over their lifespan.
Use Cases
This calculator is useful for:
Homeowners assessing the potential energy generation of a rooftop solar system.
Businesses evaluating the feasibility and return on investment for commercial solar installations.
Solar installers providing initial estimates to potential clients.
Educators and students learning about solar energy principles.
function calculateSolarOutput() {
var panelWattage = parseFloat(document.getElementById("panelWattage").value);
var panelCount = parseFloat(document.getElementById("panelCount").value);
var peakSunHours = parseFloat(document.getElementById("peakSunHours").value);
var systemLosses = parseFloat(document.getElementById("systemLosses").value);
var daysPerYear = parseFloat(document.getElementById("daysPerYear").value);
var outputDiv = document.getElementById("output");
if (isNaN(panelWattage) || isNaN(panelCount) || isNaN(peakSunHours) || isNaN(systemLosses) || isNaN(daysPerYear) ||
panelWattage <= 0 || panelCount <= 0 || peakSunHours < 0 || systemLosses 100 || daysPerYear <= 0) {
outputDiv.innerHTML = "Please enter valid positive numbers for all fields.";
outputDiv.style.color = "red";
return;
}
var totalSystemWattage = panelWattage * panelCount;
var lossFactor = 1 – (systemLosses / 100);
var dailyEnergyProductionWh = totalSystemWattage * peakSunHours * lossFactor;
var annualEnergyProductionWh = dailyEnergyProductionWh * daysPerYear;
// Convert to kWh for a more common unit
var annualEnergyProductionKwh = annualEnergyProductionWh / 1000;
outputDiv.innerHTML = annualEnergyProductionKwh.toFixed(2) + " kWh per year";
outputDiv.style.color = "#004a99"; // Reset color to default
}