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Solar Panel Savings & Payback Calculator

Your Solar Analysis

Recommended System Size –

Annual Savings –

Payback Period –

25-Year Net Profit –

function calculateSolarSavings() { var bill = parseFloat(document.getElementById('monthlyBill').value); var rate = parseFloat(document.getElementById('kwhRate').value); var sun = parseFloat(document.getElementById('sunHours').value); var cost = parseFloat(document.getElementById('installCost').value); if (isNaN(bill) || isNaN(rate) || isNaN(sun) || isNaN(cost) || rate <= 0 || sun <= 0) { alert("Please enter valid numbers in all fields."); return; } // Calculations var monthlyKwh = bill / rate; var systemSizeNeeded = monthlyKwh / (sun * 30 * 0.78); // 0.78 accounts for system inefficiency/derate factor var annualSavings = bill * 12; var paybackYears = cost / annualSavings; var totalSavings25Years = (annualSavings * 25) – cost; // Display Results document.getElementById('resSystemSize').innerText = systemSizeNeeded.toFixed(2) + " kW"; document.getElementById('resAnnualSavings').innerText = "$" + annualSavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('resPayback').innerText = paybackYears.toFixed(1) + " Years"; document.getElementById('resTotalProfit').innerText = "$" + totalSavings25Years.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('solar-results').style.display = 'block'; }

How to Use the Solar Panel Savings Calculator

Switching to renewable energy is both an environmental and a financial decision. Our solar calculator helps you estimate the return on investment (ROI) for a home solar installation by analyzing your current energy consumption and local sunlight conditions.

Key Input Definitions

• Monthly Electricity Bill: Your average expense for electricity before taxes and fixed fees.
• Electricity Rate ($/kWh): The price you pay per kilowatt-hour. You can find this on your utility statement.
• Sunlight Hours: This isn't just daylight hours, but "peak sun hours"—the intensity of sunlight that produces 1,000 watts of energy per square meter.
• Installation Cost: The total gross cost of your solar system before federal or state tax credits (ITC).

Understanding the Results

The System Size indicates the capacity of the solar array needed to offset 100% of your current bill. We include a standard 78% derate factor to account for real-world inefficiencies like wiring loss, inverter conversion, and panel soiling.

The Payback Period is the number of years it takes for your annual electricity savings to equal the initial cost of the system. In the United States, most homeowners see a payback period between 6 and 10 years, depending on local utility rates and incentives.

Example Calculation

If you spend $150 a month at a rate of $0.15/kWh, you consume 1,000 kWh monthly. In a region with 4.5 peak sun hours per day, you would need roughly an 8.2 kW system to cover your usage. If the system costs $15,000, your annual savings of $1,800 would result in a payback period of approximately 8.3 years. Over 25 years (the typical warranty life of a panel), you would save over $30,000 after paying off the equipment.