Your estimated solar system size will appear here.
Understanding Your Solar Power System Size
Determining the right size for your solar power system is crucial for maximizing energy savings and achieving your renewable energy goals. This calculator helps you estimate the required system capacity (in kilowatts, kW) based on your electricity consumption, local sunlight conditions, and desired energy offset.
How the Calculator Works:
The calculation involves a few key factors:
Average Daily Electricity Consumption (kWh): This is your household's typical energy usage per day, measured in kilowatt-hours. You can usually find this information on your utility bills.
Peak Sun Hours Per Day: This represents the average number of hours per day when sunlight is strong enough to generate significant power. This varies by geographical location and season.
System Efficiency (Derate Factor): Solar systems don't operate at 100% efficiency due to factors like panel degradation, inverter losses, wiring resistance, temperature, and shading. The derate factor (typically between 0.75 and 0.90) accounts for these losses.
Desired Energy Offset (%): This indicates the percentage of your total electricity consumption you aim to cover with solar power.
The Formula:
The core calculation follows these steps:
Calculate Target Daily Energy Production: First, we determine how much energy (in kWh) your solar system needs to produce daily to meet your desired offset.
Target Daily Production = Average Daily Consumption * (Desired Offset / 100)
Calculate Required System Capacity (kW): Then, we adjust for peak sun hours and system efficiency to find the necessary system size.
System Size (kW) = Target Daily Production / (Peak Sun Hours * System Efficiency)
In this example, you would need approximately a 7.06 kW solar system to offset 90% of your daily electricity consumption under these conditions.
Factors Influencing System Size:
Roof Space and Orientation: The available area and the direction your roof faces impact how many panels you can install and how effectively they capture sunlight.
Shading: Trees, neighboring buildings, or other obstructions can significantly reduce solar production.
Panel Wattage: Modern solar panels come in various wattages (e.g., 300W, 400W). The total system size is the sum of the wattages of all installed panels.
Battery Storage: If you plan to store excess energy for use at night or during outages, this may influence the overall system design and capacity.
Future Energy Needs: Consider potential increases in electricity usage (e.g., electric vehicles, new appliances).
Consulting with a professional solar installer is highly recommended. They can perform a site assessment, provide a precise system design, and offer tailored recommendations based on your specific circumstances.
function calculateSystemSize() {
var avgDailyConsumption = parseFloat(document.getElementById("averageDailyConsumption").value);
var peakSunHours = parseFloat(document.getElementById("peakSunHours").value);
var systemEfficiency = parseFloat(document.getElementById("systemEfficiency").value);
var desiredOffset = parseFloat(document.getElementById("desiredOffset").value);
var resultDiv = document.getElementById("result");
// Input validation
if (isNaN(avgDailyConsumption) || isNaN(peakSunHours) || isNaN(systemEfficiency) || isNaN(desiredOffset)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (avgDailyConsumption <= 0 || peakSunHours <= 0 || systemEfficiency <= 0 || desiredOffset 100) {
resultDiv.innerHTML = "Please enter positive values for consumption, sun hours, efficiency, and an offset between 0 and 100%.";
return;
}
if (systemEfficiency > 1) {
resultDiv.innerHTML = "System efficiency should typically be a value between 0 and 1 (e.g., 0.85 for 85%).";
return;
}
// Calculations
var targetDailyProduction = avgDailyConsumption * (desiredOffset / 100);
var systemSizeKW = targetDailyProduction / (peakSunHours * systemEfficiency);
// Display result
resultDiv.innerHTML = "Estimated Solar System Size: " + systemSizeKW.toFixed(2) + " kW";
}