Investing in solar panels is a significant decision, and understanding the potential return on investment (ROI) is crucial. This calculator helps you estimate the financial viability of a solar panel system by considering its initial cost, ongoing savings, incentives, maintenance, and expected lifespan.
How the Calculation Works:
The calculator uses the following formulas:
Net Investment Cost = Total System Cost – Total Solar Incentives & Rebates
Total Savings Over Lifespan = Estimated Annual Electricity Savings * System Lifespan
Total Maintenance Costs Over Lifespan = Estimated Annual Maintenance Cost * System Lifespan
Total Net Profit Over Lifespan = Total Savings Over Lifespan – Total Maintenance Costs Over Lifespan – Net Investment Cost
Simple Payback Period = Net Investment Cost / Estimated Annual Electricity Savings (assuming annual savings are constant and greater than annual maintenance costs)
Return on Investment (ROI) = (Total Net Profit Over Lifespan / Net Investment Cost) * 100%
Key Inputs Explained:
Total System Cost ($): The upfront price you pay for the solar panel system, including installation.
Estimated Annual Electricity Savings ($): The amount you expect to save on your electricity bills each year after installing solar panels. This can vary based on your energy consumption, panel efficiency, and local electricity rates.
Total Solar Incentives & Rebates ($): Any grants, tax credits, or rebates offered by government or local programs that reduce the overall cost of your solar investment.
Estimated Annual Maintenance Cost ($): Ongoing costs associated with keeping your solar system in good working order, such as cleaning, inspections, or minor repairs.
System Lifespan (Years): The expected operational life of your solar panel system, typically 25-30 years.
Interpreting the Results:
Net Investment Cost: This is the true cost of your solar system after accounting for immediate financial incentives.
Total Savings Over Lifespan: The cumulative amount you'll save on electricity bills over the system's life.
Total Maintenance Costs Over Lifespan: The total expected expenditure on upkeep.
Total Net Profit Over Lifespan: The total financial gain you can expect from the system over its entire operational period. A positive number indicates profitability.
Simple Payback Period: The time it takes for the accumulated electricity savings to equal the initial net investment. A shorter payback period generally indicates a more attractive investment.
Return on Investment (ROI): This percentage shows the profitability of your solar investment relative to its net cost. A higher ROI signifies a more financially rewarding investment.
Disclaimer: This calculator provides an estimate based on the inputs provided. Actual savings and costs can vary significantly due to factors like weather patterns, electricity price fluctuations, system degradation, and unforeseen maintenance. Consult with solar professionals for a personalized assessment.
function calculateROI() {
var systemCost = parseFloat(document.getElementById("systemCost").value);
var annualSavings = parseFloat(document.getElementById("annualSavings").value);
var incentives = parseFloat(document.getElementById("incentives").value);
var annualMaintenance = parseFloat(document.getElementById("annualMaintenance").value);
var systemLifespan = parseFloat(document.getElementById("systemLifespan").value);
var netInvestment = document.getElementById("netInvestment");
var totalSavingsLifespan = document.getElementById("totalSavingsLifespan");
var totalMaintenance = document.getElementById("totalMaintenance");
var totalNetProfit = document.getElementById("totalNetProfit");
var paybackPeriod = document.getElementById("paybackPeriod");
var roiPercentage = document.getElementById("roiPercentage");
// Clear previous results
netInvestment.textContent = "–";
totalSavingsLifespan.textContent = "–";
totalMaintenance.textContent = "–";
totalNetProfit.textContent = "–";
paybackPeriod.textContent = "–";
roiPercentage.textContent = "–";
// Validate inputs
if (isNaN(systemCost) || systemCost <= 0 ||
isNaN(annualSavings) || annualSavings < 0 ||
isNaN(incentives) || incentives < 0 ||
isNaN(annualMaintenance) || annualMaintenance < 0 ||
isNaN(systemLifespan) || systemLifespan 0) {
calculatedPaybackPeriod = calculatedNetInvestment / annualSavings;
} else {
calculatedPaybackPeriod = Infinity; // Cannot payback if no savings
}
var calculatedRoiPercentage;
if (calculatedNetInvestment > 0) {
calculatedRoiPercentage = (calculatedTotalNetProfit / calculatedNetInvestment) * 100;
} else if (calculatedNetInvestment === 0 && calculatedTotalNetProfit > 0) {
calculatedRoiPercentage = Infinity; // Infinite ROI if no cost and profit
} else if (calculatedNetInvestment === 0 && calculatedTotalNetProfit <= 0) {
calculatedRoiPercentage = 0; // Zero ROI if no cost and no profit/loss
}
else {
calculatedRoiPercentage = -100; // Assuming full loss if net investment is negative and profit is also negative or zero
}
netInvestment.textContent = "$" + calculatedNetInvestment.toFixed(2);
totalSavingsLifespan.textContent = "$" + calculatedTotalSavingsLifespan.toFixed(2);
totalMaintenance.textContent = "$" + calculatedTotalMaintenance.toFixed(2);
totalNetProfit.textContent = "$" + calculatedTotalNetProfit.toFixed(2);
paybackPeriod.textContent = calculatedPaybackPeriod === Infinity ? "N/A" : calculatedPaybackPeriod.toFixed(2);
roiPercentage.textContent = calculatedRoiPercentage === Infinity ? "Infinite" : (calculatedRoiPercentage === -100 ? "Loss" : calculatedRoiPercentage.toFixed(2));
}