Mortgage Rate Calculator 15 Year Fixed

Solar Panel ROI & Payback Calculator

Calculation Summary

Net System Cost:

Annual Savings:

Payback Period:

25-Year Net Profit:

function calculateSolarROI() { var size = parseFloat(document.getElementById('systemSize').value); var sun = parseFloat(document.getElementById('sunHours').value); var rate = parseFloat(document.getElementById('elecRate').value); var cost = parseFloat(document.getElementById('installCost').value); var credit = parseFloat(document.getElementById('taxCredit').value); if (isNaN(size) || isNaN(sun) || isNaN(rate) || isNaN(cost) || isNaN(credit)) { alert("Please fill in all fields with valid numbers."); return; } // Calculations var efficiencyFactor = 0.78; // Accounts for inverter loss, wiring, and panel degradation var annualProduction = size * sun * 365 * efficiencyFactor; var annualSavings = annualProduction * rate; var netCost = cost – (cost * (credit / 100)); var paybackPeriod = netCost / annualSavings; var twentyFiveYearSavings = (annualSavings * 25) – netCost; // Formatting document.getElementById('resNetCost').innerText = '$' + netCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('resAnnualSavings').innerText = '$' + annualSavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('resPayback').innerText = paybackPeriod.toFixed(1) + ' Years'; document.getElementById('resProfit').innerText = '$' + twentyFiveYearSavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('solar-results').style.display = 'block'; }

Understanding Your Solar Return on Investment

Switching to solar energy is one of the most significant financial decisions a homeowner can make. While the environmental benefits are clear, the financial "Payback Period" and "Return on Investment" (ROI) are the primary drivers for most installations. This calculator helps you determine exactly how long it will take for your system to pay for itself and how much you can expect to save over the 25-year lifespan of the panels.

Key Variables in Solar Math

• System Size (kW): The total capacity of your panels. A typical US home requires a 6kW to 10kW system.
• Average Daily Sun Hours: This is not just daylight, but "peak sun hours" where the sun's intensity reaches 1,000 watts per square meter. In the US, this ranges from 3.5 in the North to 6+ in the Southwest.
• The Federal Solar Tax Credit (ITC): As of 2024, the federal government offers a 30% tax credit on the total cost of installation, which significantly reduces your net investment.
• System Efficiency: No system is 100% efficient. Factors like heat, dust, and DC-to-AC conversion loss typically result in an efficiency factor of about 75% to 80%.

How the Calculation Works

To find your annual savings, we use the following formula:

(System Size × Daily Sun Hours × 365 Days × 0.78 Efficiency) × Electricity Rate = Annual Savings

The Payback Period is then determined by dividing your Net Cost (Total price minus tax credits) by your Annual Savings.

Real-World Example

Imagine a homeowner in Florida installing an 8kW system:

• Install Cost: $24,000
• 30% Tax Credit: -$7,200
• Net Investment: $16,800
• Sun Hours: 5.5 hours/day
• Savings: At $0.15/kWh, this system generates roughly $1,870 in electricity per year.
• Result: A payback period of approximately 9 years, followed by 16+ years of free electricity.

Frequently Asked Questions

Does solar increase my property value?
Yes, studies by Zillow and Lawrence Berkeley National Laboratory show that solar installations can increase home value by an average of 4% or roughly $4,000 to $6,000 per kilowatt of solar installed.

What is the typical lifespan of a system?
Most modern solar panels are warrantied for 25 years. However, they often continue to produce power at a slightly reduced capacity (80-85% of original power) for 30 to 40 years.

Do I still have an electric bill?
Unless you have a battery backup system (like a Tesla Powerwall) and go entirely off-grid, you will still be connected to the utility. If your system produces more than you use during the day, "Net Metering" allows you to bank those credits for use at night.