This calculator helps you estimate the daily and annual energy production of your solar panel system. Solar energy systems are a fantastic way to reduce your carbon footprint and electricity bills. The amount of energy a solar panel system can generate depends on several key factors, including the size and efficiency of the panels, the amount of sunlight they receive, and system losses.
The Calculation Formula
The core calculation for estimating daily energy production is as follows:
Daily Energy Output (kWh) = (Total Panel Wattage (Wp) * Peak Sun Hours per Day * System Efficiency Factor) / 1000
Breakdown of Components:
Total Panel Wattage (Wp): This is the combined power output of all your solar panels under Standard Test Conditions (STC). It's calculated by multiplying the wattage of a single panel by the number of panels. For example, if you have 10 panels, each rated at 300 Wp, your total is 3000 Wp.
Peak Sun Hours per Day: This isn't the total hours of daylight, but rather the equivalent number of hours per day where solar irradiance averages 1000 W/m² (the standard for panel testing). This value varies significantly by location and season. A common estimate for many regions is between 4 to 6 hours.
System Efficiency Factor (or Loss Factor): Solar systems are not 100% efficient. Energy is lost due to factors like shading, dust, temperature, inverter efficiency, and wiring. A typical system loss factor ranges from 0.75 to 0.90 (meaning 10-25% loss). We use this as a multiplier; a value of 0.85 represents an 85% system efficiency.
Division by 1000: This converts the result from Watt-hours (Wh) to kilowatt-hours (kWh), which is the standard unit for measuring electricity consumption and production.
Estimating Annual Output
To estimate the annual energy output, you simply multiply the calculated daily output by the number of days in a year (365):
Annual Energy Output (kWh) = Daily Energy Output (kWh) * 365
Factors Affecting Performance
Location: Geographic location significantly impacts the amount of direct sunlight received.
Panel Orientation and Tilt: Panels facing directly towards the equator (south in the Northern Hemisphere, north in the Southern Hemisphere) at an optimal tilt angle will perform best.
Shading: Even partial shading on a single panel can reduce the output of the entire string in some systems.
Weather: Cloudy days, fog, and heavy rain will reduce energy production.
Temperature: Solar panels tend to become slightly less efficient as their temperature increases.
Maintenance: Keeping panels clean from dust, dirt, and debris is crucial for optimal performance.
This calculator provides a valuable estimate for planning and understanding your solar energy potential. For precise figures, consult with a professional solar installer who can perform a site-specific assessment.
function calculateEnergy() {
var panelWattage = parseFloat(document.getElementById("panelWattage").value);
var numberOfPanels = parseFloat(document.getElementById("numberOfPanels").value);
var peakSunHours = parseFloat(document.getElementById("peakSunHours").value);
var systemLossFactor = parseFloat(document.getElementById("systemLossFactor").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = "; // Clear previous results
// Input validation
if (isNaN(panelWattage) || panelWattage <= 0) {
resultDiv.innerHTML = 'Please enter a valid Solar Panel Wattage (must be positive).';
return;
}
if (isNaN(numberOfPanels) || numberOfPanels <= 0) {
resultDiv.innerHTML = 'Please enter a valid Number of Panels (must be positive).';
return;
}
if (isNaN(peakSunHours) || peakSunHours <= 0) {
resultDiv.innerHTML = 'Please enter valid Peak Sun Hours per Day (must be positive).';
return;
}
if (isNaN(systemLossFactor) || systemLossFactor 1) {
resultDiv.innerHTML = 'Please enter a valid System Loss Factor between 0.0 and 1.0.';
return;
}
var totalPanelWattage = panelWattage * numberOfPanels;
var dailyEnergyWh = totalPanelWattage * peakSunHours * systemLossFactor;
var dailyEnergyKwh = dailyEnergyWh / 1000;
var annualEnergyKwh = dailyEnergyKwh * 365;
resultDiv.innerHTML = 'Estimated Daily Output: ' + dailyEnergyKwh.toFixed(2) + ' kWh' +
'Estimated Annual Output: ' + annualEnergyKwh.toFixed(2) + ' kWh';
}