Mileage and Fuel Cost Calculator

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Solar Panel ROI Calculator

Investment Analysis

Estimated Annual Production

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Annual Cost Savings

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Payback Period

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Total 25-Year Profit

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25-Year ROI: —

function calculateSolarROI() { var systemCost = parseFloat(document.getElementById('systemCost').value) || 0; var systemSize = parseFloat(document.getElementById('systemSize').value) || 0; var monthlyBill = parseFloat(document.getElementById('monthlyBill').value) || 0; var elecRate = parseFloat(document.getElementById('elecRate').value) || 0; var sunHours = parseFloat(document.getElementById('sunHours').value) || 0; var incentives = parseFloat(document.getElementById('incentives').value) || 0; if (systemCost <= 0 || systemSize <= 0) { alert("Please enter valid system cost and size."); return; } // Calculation Logic // Estimated annual production = Size (kW) * Sun Hours * 365 * 0.78 (Derate factor for efficiency losses) var annualKwh = systemSize * sunHours * 365 * 0.78; // Annual Savings based on production and rate var annualSavings = annualKwh * elecRate; // Net Cost after incentives var netCost = systemCost – incentives; // Payback Period (Years) var payback = netCost / annualSavings; // 25-Year totals (typical panel lifespan) // Assuming 0.5% annual degradation and 3% annual electricity price inflation var totalSavings25 = 0; var currentYearSavings = annualSavings; for (var i = 0; i < 25; i++) { totalSavings25 += currentYearSavings; currentYearSavings = currentYearSavings * 1.03 * 0.995; } var totalProfit = totalSavings25 – netCost; var roi = (totalProfit / netCost) * 100; // Display results document.getElementById('annualProd').innerHTML = Math.round(annualKwh).toLocaleString() + " kWh"; document.getElementById('annualSavings').innerHTML = "$" + Math.round(annualSavings).toLocaleString(); document.getElementById('paybackPeriod').innerHTML = payback.toFixed(1) + " Years"; document.getElementById('totalProfit').innerHTML = "$" + Math.round(totalProfit).toLocaleString(); document.getElementById('roiPercent').innerHTML = Math.round(roi) + "%"; document.getElementById('solarResult').style.display = 'block'; }

How to Calculate Your Solar Panel ROI

Switching to solar energy is a significant financial decision. Understanding your Return on Investment (ROI) helps you determine if the initial capital outlay is worth the long-term savings on your utility bills. Our calculator considers the size of your system, local sunlight conditions, and financial incentives to provide a clear picture of your potential savings.

Key Factors Influencing Your Solar Payback

  • Gross System Cost: This is the total price for equipment, labor, permitting, and grid connection before any discounts or tax credits.
  • The Federal Investment Tax Credit (ITC): In many regions, governments offer substantial tax credits (such as the 30% federal credit in the U.S.) that significantly lower the net cost.
  • Solar Irradiance: The amount of peak sunlight hours your roof receives. A 7kW system in Arizona will produce significantly more power than the same system in Washington state.
  • Electricity Rates: The higher your current utility rate ($/kWh), the more money you save for every kilowatt-hour your panels produce.

Example Calculation

Imagine a homeowner in California who installs a 6kW system costing $18,000. After a 30% Federal Tax Credit ($5,400), the net cost is $12,600.

If the system produces 9,000 kWh per year and the local electricity rate is $0.22/kWh, the annual savings would be approximately $1,980. Dividing the net cost ($12,600) by the annual savings ($1,980) results in a payback period of roughly 6.3 years.

Long-term Value and Degradation

Most modern solar panels come with a 25-year performance warranty. While efficiency slightly decreases over time (usually about 0.5% per year), the rising cost of grid electricity often offsets this degradation, leading to increased savings in the later years of the system's life. Solar panels also typically increase the resale value of a home, which is an "invisible" ROI factor not captured in monthly bill savings.

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