4.5Average daily hours of direct sunlight equivalent to 1000 W/m². Varies by location and season.
15Percentage reduction in output due to shading, dirt, temperature, inverter efficiency, etc.
Estimated Daily Energy Output
—kWh
Understanding Solar Panel Power Output
This calculator helps estimate the daily energy production of a solar photovoltaic (PV) system. Solar panels convert sunlight into electricity, but their output is influenced by several factors. Understanding these factors allows for more accurate estimations and better system design.
How the Calculation Works
The calculation is based on a simplified model that takes into account the key parameters of your solar installation:
Panel Wattage (Wp): This is the rated power output of a single solar panel under Standard Test Conditions (STC). STC involves an irradiance of 1000 W/m², an ambient temperature of 25°C, and an air mass of 1.5.
Number of Panels: The total capacity of your solar system is directly proportional to the number of panels installed.
Peak Sun Hours per Day: This metric represents the equivalent number of hours per day when solar irradiance averages 1000 W/m². It's not the same as total daylight hours; it accounts for the intensity of sunlight. For example, 8 hours of daylight with varying cloud cover and sun angle might only equate to 4.5 peak sun hours.
System Losses: Real-world performance is always lower than the theoretical maximum due to various factors like:
Inverter Efficiency: Converting DC power from panels to AC power for your home.
Temperature Effects: Panel efficiency decreases as temperature rises.
Shading: Even partial shading can significantly reduce output.
Dirt and Soiling: Accumulation of dust and debris on panels.
Wiring and Connection Losses: Resistance in electrical components.
Module Degradation: Natural decrease in panel performance over time.
The system losses percentage accounts for these combined effects.
The formula used is:
Daily Energy Output (kWh) = (Panel Wattage (Wp) × Number of Panels) × Peak Sun Hours × (1 – System Losses Percentage / 100)
For example, if you have 10 panels, each rated at 400 Wp, with 4.5 peak sun hours and 15% system losses:
Total System Capacity = 400 Wp × 10 panels = 4000 Wp = 4 kWp
The calculated value is an estimate. Actual energy production can vary based on:
Geographic Location: Different regions receive varying amounts of sunlight.
Panel Orientation and Tilt: The angle and direction panels face significantly impact energy capture.
Weather Conditions: Cloud cover, temperature, and humidity on any given day.
Age of the System: Solar panels degrade over time, typically losing 0.5% to 1% of their capacity per year.
Maintenance: Regular cleaning and system checks can optimize performance.
Use Cases
This calculator is useful for:
Homeowners considering solar panel installation to estimate potential energy generation.
System designers performing preliminary calculations.
Individuals wanting to understand the basic energy output of a given solar setup.
Comparing the potential output of different system sizes or locations.
function calculateSolarPower() {
var panelWattage = parseFloat(document.getElementById("panelWattage").value);
var numberOfPanels = parseFloat(document.getElementById("numberOfPanels").value);
var peakSunHours = parseFloat(document.getElementById("peakSunHours").value);
var systemLosses = parseFloat(document.getElementById("systemLosses").value);
var isValid = true;
if (isNaN(panelWattage) || panelWattage <= 0) {
alert("Please enter a valid Panel Wattage (greater than 0).");
isValid = false;
}
if (isNaN(numberOfPanels) || numberOfPanels <= 0) {
alert("Please enter a valid Number of Panels (greater than 0).");
isValid = false;
}
if (isNaN(peakSunHours) || peakSunHours < 0) {
alert("Please enter a valid Peak Sun Hours (0 or greater).");
isValid = false;
}
if (isNaN(systemLosses) || systemLosses 100) {
alert("Please enter a valid System Losses percentage (between 0 and 100).");
isValid = false;
}
if (isValid) {
var totalSystemWattPeak = panelWattage * numberOfPanels;
var lossFactor = 1 – (systemLosses / 100);
var dailyEnergyOutput = totalSystemWattPeak * peakSunHours * lossFactor;
// Convert Wp to kWp for calculation clarity
var totalSystemKiloWattPeak = totalSystemWattPeak / 1000;
// Display the result in kWh
document.getElementById("result-value").innerText = dailyEnergyOutput.toFixed(2);
document.getElementById("result-unit").innerText = "kWh per day";
}
}