Solar Panel Savings Calculator
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Solar Panel Savings Calculator
Estimated Savings
$0.00
Payback Period: N/A
Estimated Lifetime Savings (25 Years): $0.00
Understanding Your Solar Panel Savings
Investing in solar panels is a significant decision that can lead to substantial long-term financial benefits. This calculator helps you estimate the potential savings and payback period for a residential solar panel system based on key factors like system size, energy production, electricity costs, and system expenses.
How the Calculator Works:
The calculator uses the following logic to provide your estimated savings:
- Annual Electricity Production: The total energy your solar system is expected to generate in a year. This is calculated by multiplying the System Size (kW) by the Estimated Annual Production (kWh per kW).
Formula: Annual Production (kWh) = System Size (kW) * Annual Production per kW (kWh/kW)
- Annual Savings (Year 1): The amount of money you save in the first year by generating your own electricity. This is calculated by multiplying the Annual Electricity Production (kWh) by your Current Electricity Cost ($/kWh).
Formula: Annual Savings (Year 1) = Annual Production (kWh) * Electricity Cost ($/kWh)
- Net System Cost: The actual upfront cost you pay for the system after accounting for any incentives or rebates.
Formula: Net System Cost ($) = Total System Cost ($) – Solar Incentives/Rebates ($)
- Payback Period: The time it takes for your cumulative savings to equal your net system cost. This is estimated by dividing the Net System Cost ($) by the Annual Savings (Year 1). Note that this is a simplified calculation and doesn't account for system degradation or increasing electricity prices in early years.
Formula: Payback Period (Years) = Net System Cost ($) / Annual Savings (Year 1) ($/Year)
- Lifetime Savings (25 Years): This estimates your total savings over a typical 25-year lifespan of a solar panel system. It considers the initial annual savings and accounts for the gradual decrease in energy production due to Annual System Degradation. The electricity cost is assumed to remain constant for this simplified calculation, but in reality, it may increase.
Calculation: Sum of (Annual Production * Electricity Cost) for each year, adjusting production by degradation.
Key Input Factors:
- System Size (kW): The total capacity of your solar panel installation. Larger systems generate more electricity but cost more.
- Estimated Annual Production (kWh per kW): This metric reflects how much energy (in kilowatt-hours) 1 kilowatt of solar capacity typically produces in your specific location, considering factors like sunlight hours and panel efficiency.
- Your Current Electricity Cost ($/kWh): The rate you pay your utility company for electricity. Higher electricity costs mean greater potential savings from solar.
- Total System Cost ($): The gross price of purchasing and installing the solar panel system.
- Solar Incentives/Rebates ($): Any government tax credits, local rebates, or other financial incentives that reduce the upfront cost of the system.
- Annual System Degradation (%): Solar panels naturally lose a small amount of efficiency each year. This accounts for that decline.
Important Considerations:
- This calculator provides an estimate. Actual savings can vary based on installation quality, weather patterns, system maintenance, shading, and changes in electricity rates.
- The payback period is a critical metric, but consider the long-term benefits of reduced carbon footprint and energy independence.
- Consult with reputable solar installers for personalized quotes and more precise performance estimates for your specific roof and location.
function calculateSavings() {
var systemSize = parseFloat(document.getElementById("systemSize").value);
var annualProductionPerKw = parseFloat(document.getElementById("annualProduction").value);
var electricityCost = parseFloat(document.getElementById("electricityCost").value);
var systemCost = parseFloat(document.getElementById("systemCost").value);
var annualDegradation = parseFloat(document.getElementById("annualDegradation").value) / 100; // Convert percentage to decimal
var incentiveValue = parseFloat(document.getElementById("incentiveValue").value);
// Input validation
if (isNaN(systemSize) || systemSize <= 0 ||
isNaN(annualProductionPerKw) || annualProductionPerKw <= 0 ||
isNaN(electricityCost) || electricityCost < 0 || // Electricity cost can be 0 if free
isNaN(systemCost) || systemCost < 0 ||
isNaN(annualDegradation) || annualDegradation 1 ||
isNaN(incentiveValue) || incentiveValue 0) {
paybackPeriod = (netSystemCost / firstYearSavings).toFixed(1) + " years";
} else if (netSystemCost <= 0) {
paybackPeriod = "0.0 years (Cost covered by incentives)";
} else {
paybackPeriod = "Infinite (Savings too low)";
}
// Calculate lifetime savings over 25 years
var lifetimeSavings = 0;
var currentYearProductionFactor = 1;
for (var year = 0; year < 25; year++) {
lifetimeSavings += annualProductionKwh * currentYearProductionFactor * electricityCost;
currentYearProductionFactor *= (1 – annualDegradation);
}
lifetimeSavings = Math.max(0, lifetimeSavings – netSystemCost); // Ensure savings don't go below zero after cost deduction
document.getElementById("annualSavings").textContent = "$" + firstYearSavings.toFixed(2);
document.getElementById("paybackPeriod").textContent = "Payback Period: " + paybackPeriod;
document.getElementById("lifetimeSavings").textContent = "Estimated Lifetime Savings (25 Years): $" + lifetimeSavings.toFixed(2);
}