Calculate the required solar panel system size (in Watts) based on your daily energy consumption and location's solar irradiance.
This varies by location and season. Search online for your region's average.
Accounts for energy losses due to shading, dust, temperature, wiring, etc. Typically 0.75 to 0.90.
Required System Size:
— W
Understanding Solar Energy System Sizing
Sizing a solar energy system is crucial for ensuring it meets your electricity needs efficiently. This calculator helps estimate the total DC (Direct Current) power capacity of the solar array required to meet your average daily energy consumption.
The Formula Explained
The core calculation is derived from the relationship between energy consumption, available sunlight, and system efficiency:
Daily Energy Consumption (kWh) = System Size (kW) * Peak Sun Hours * System Loss Factor
To find the required system size (in kW), we rearrange the formula:
System Size (kW) = Daily Energy Consumption (kWh) / (Peak Sun Hours * System Loss Factor)
Where:
Average Daily Energy Consumption (kWh): This is the total amount of electricity your household or business uses on an average day. You can find this information on your electricity bills, typically listed in kilowatt-hours (kWh) per month. Divide your monthly usage by the number of days in the month to get the daily average.
Average Peak Sun Hours per Day: This represents the equivalent number of hours per day when solar irradiance averages 1,000 watts per square meter. This metric is specific to your geographical location and accounts for variations in sunlight intensity throughout the day and year. It's not the same as the total number of daylight hours. You can usually find this data from solar resource maps or online databases for your specific region.
System Loss Factor: Solar energy systems are not 100% efficient. Various factors contribute to energy loss, including:
Temperature: Solar panels operate less efficiently at higher temperatures.
Shading: Obstructions like trees or buildings can block sunlight.
Dirt and Dust: Accumulation on panels reduces light absorption.
Inverter Efficiency: The process of converting DC to AC electricity has losses.
Wiring Losses: Resistance in cables causes minor energy dissipation.
Panel Degradation: Solar panels gradually lose efficiency over time.
A typical system loss factor ranges from 0.75 (representing 25% loss) to 0.90 (representing 10% loss). The default value of 0.85 (15% loss) is a common starting point.
Interpreting the Results
The calculator outputs the required DC system size in Watts (W). This is the total rated power of the solar panels. For example, if the calculator shows 5000 W, you would need a system with a combined panel output of 5 kilowatts (kW).
Important Considerations:
This calculator provides an estimate. A professional solar installer will conduct a detailed site assessment to provide a precise system design.
Oversizing your system might lead to unnecessary costs, while undersizing means you won't meet your energy goals.
Local regulations, available roof space, and your budget will also influence the final system size.
Consider future energy needs, such as purchasing an electric vehicle or installing more appliances.
function calculateSolarSize() {
var dailyKwh = parseFloat(document.getElementById("dailyKwh").value);
var peakSunHours = parseFloat(document.getElementById("peakSunHours").value);
var systemLossFactor = parseFloat(document.getElementById("systemLossFactor").value);
var resultValueElement = document.getElementById("result-value");
var resultMessageElement = document.getElementById("result-message");
// Clear previous messages
resultValueElement.textContent = "– W";
resultMessageElement.textContent = "";
// Validate inputs
if (isNaN(dailyKwh) || isNaN(peakSunHours) || isNaN(systemLossFactor)) {
resultMessageElement.textContent = "Please enter valid numbers for all fields.";
resultMessageElement.style.color = "red";
return;
}
if (dailyKwh <= 0 || peakSunHours <= 0 || systemLossFactor 1) {
resultMessageElement.textContent = "Please enter positive values. System Loss Factor must be between 0 and 1.";
resultMessageElement.style.color = "red";
return;
}
// Calculate required system size in kW
// System Size (kW) = Daily Energy Consumption (kWh) / (Peak Sun Hours * System Loss Factor)
var systemSizeKw = dailyKwh / (peakSunHours * systemLossFactor);
// Convert kW to Watts
var systemSizeWatts = systemSizeKw * 1000;
// Display the result
resultValueElement.textContent = systemSizeWatts.toFixed(2) + " W";
resultValueElement.style.color = "#28a745"; // Success Green
// Add a helpful message
resultMessageElement.textContent = "This is the estimated DC power capacity needed. Consult a solar professional for a detailed assessment.";
resultMessageElement.style.color = "#333";
}