Investing in a solar rooftop system is a significant decision that can lead to substantial long-term savings and environmental benefits. This calculator helps you estimate the potential of a solar installation for your home or business. It considers key factors like your energy consumption, local sunlight availability, system efficiency, and the current cost of electricity.
How the Calculator Works:
The calculator estimates two primary outputs: the optimal solar system size and the potential annual savings.
1. Estimated Solar System Size (kW):
This is often determined by a combination of your annual electricity usage and the available sunlight hours. A larger system will generate more electricity, but also incurs a higher upfront cost. The calculator uses your inputs to suggest a suitable system size that could potentially offset a significant portion of your energy needs.
2. Estimated Annual Electricity Generation (kWh):
This is calculated using the following formula:
Annual Generation (kWh) = System Size (kW) × Average Daily Sunlight Hours × 365 days/year × System Efficiency
For example, an 8 kW system with 5 average daily sunlight hours and 85% efficiency would generate approximately:
8 kW × 5 hours/day × 365 days/year × 0.85 = 12410 kWh per year
3. Potential Annual Savings ($):
This is a projection of how much money you could save on your electricity bills. It's calculated by comparing the electricity your solar system generates to your annual consumption and multiplying the offset by the price you pay for electricity.
Annual Savings ($) = Offset Energy (kWh) × Average Electricity Price ($/kWh)
If your system generates 12410 kWh and your usage is 10000 kWh, with electricity at $0.15/kWh, your savings would be:
MIN(12410 kWh, 10000 kWh) × $0.15/kWh = 10000 kWh × $0.15/kWh = $1500 per year
4. Estimated System Cost ($):
This provides an estimate of the total cost of installing the suggested solar system.
System Cost ($) = System Size (kW) × 1000 (to convert kW to W) × Cost per Watt ($/W)
For an 8 kW system with a cost of $3.00 per Watt:
8 kW × 1000 W/kW × $3.00/W = $24,000
Factors Affecting Performance:
Shading: Trees or buildings that cast shadows on your roof can significantly reduce energy output.
Panel Degradation: Solar panels degrade slightly over time, typically by about 0.5% per year.
Weather: Cloudy days, snow, and extreme heat can impact generation.
Roof Condition and Orientation: The angle and direction of your roof, as well as its condition, play a role in installation feasibility and performance.
Local Regulations and Incentives: Government rebates, tax credits, and net metering policies can substantially affect the overall financial picture.
This calculator provides an estimate for informational purposes. For precise figures, consult with a professional solar installer who can conduct a site-specific assessment.
function calculateSolar() {
var annualElectricityUsage = parseFloat(document.getElementById("annualElectricityUsage").value);
var averageSunlightHours = parseFloat(document.getElementById("averageSunlightHours").value);
var systemEfficiency = parseFloat(document.getElementById("systemEfficiency").value);
var solarSystemSize = parseFloat(document.getElementById("solarSystemSizeSlider").value); // Using slider value directly
var costPerWatt = parseFloat(document.getElementById("costPerWatt").value);
var electricityPrice = parseFloat(document.getElementById("electricityPrice").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(annualElectricityUsage) || isNaN(averageSunlightHours) || isNaN(systemEfficiency) || isNaN(solarSystemSize) || isNaN(costPerWatt) || isNaN(electricityPrice)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (annualElectricityUsage <= 0 || averageSunlightHours <= 0 || systemEfficiency <= 0 || solarSystemSize <= 0 || costPerWatt <= 0 || electricityPrice 1) {
resultDiv.innerHTML = "System efficiency should be a value between 0 and 1 (e.g., 0.85 for 85%).";
return;
}
// Calculations
var annualGeneration = solarSystemSize * averageSunlightHours * 365 * systemEfficiency;
var offsetEnergy = Math.min(annualGeneration, annualElectricityUsage);
var annualSavings = offsetEnergy * electricityPrice;
var systemCost = solarSystemSize * 1000 * costPerWatt; // kW to W conversion
var formattedSavings = annualSavings.toFixed(2);
var formattedGeneration = annualGeneration.toFixed(0);
var formattedSystemCost = systemCost.toFixed(2);
var formattedSystemSize = solarSystemSize.toFixed(1); // Display system size with one decimal place
resultDiv.innerHTML =
"
Your Estimated Results
" +
"
Estimated System Size: " + formattedSystemSize + " kW
Estimated System Cost: $" + formattedSystemCost + "
";
}
// Initial update for slider value display
document.addEventListener('DOMContentLoaded', function() {
var slider = document.getElementById("solarSystemSizeSlider");
var valueSpan = document.getElementById("solarSystemSizeValue");
valueSpan.innerText = slider.value;
// Trigger calculation on load if desired, or wait for button click
// calculateSolar();
});