Solar Panel Calculator
Estimate solar panel output, savings, payback period, and ROI. Includes federal tax credit and 25-year projections.
System Parameters
Financial Inputs
System Size
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kW
Annual Output
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kWh/year
Year 1 Savings
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$/year
System Cost
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after tax credit
Payback Period
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years
25-Year Savings
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total
25-Year ROI
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%
CO2 Offset
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tonnes/year
Equiv. Trees
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planted
Cumulative Savings vs. System Cost
Estimated Monthly Output
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Book a Free ConsultationHow to Use This Solar Panel Calculator
This free solar panel calculator helps homeowners, businesses, and energy professionals quickly estimate the output, savings, and return on investment of a rooftop solar installation. Simply enter your available roof area, select your region for average peak sun hours, and adjust financial parameters like electricity rate and system cost to see instant results.
Understanding Your Results
System size is calculated from your roof area converted to square meters, multiplied by panel efficiency. A typical residential panel converts 18-22% of incident sunlight into electricity. Annual output accounts for peak sun hours in your region and an 80% system loss factor that covers inverter efficiency, wiring losses, shading, soiling, and temperature derating.
The payback period shows how many years until your cumulative electricity savings exceed the net system cost after applying the federal Investment Tax Credit (ITC). The 25-year projection includes annual panel degradation (typically 0.5%/year) and a 3% annual electricity price escalation based on U.S. historical averages, discounted at a 5% rate for the NPV calculation.
Federal Solar Tax Credit (ITC)
The federal Investment Tax Credit allows you to deduct a percentage of your solar installation cost from your federal taxes. As of 2024, the ITC is 30% for residential and commercial systems installed through 2032. This significantly reduces payback periods and improves ROI. State and local incentives may further reduce your net cost.
The CO2 offset is estimated using the U.S. grid average emissions factor of 0.42 kg CO2 per kWh. Your actual carbon savings depend on your local grid mix. Each tonne of CO2 offset is roughly equivalent to planting 50 trees, providing a tangible way to understand your environmental impact.