Solar Panel Calculator
Calculate solar panel system size, costs, savings, and payback period. Includes federal tax credit and environmental impact estimates.
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Last updated: January 2026
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Frequently Asked Questions
How many solar panels do I need for my home?
The number depends on your energy usage and panel wattage. Average US home uses 10,500 kWh/year. With 400W panels producing ~1.6 kWh/day (4 peak sun hours), you'd need about 18-22 panels for a 7-8 kW system. Formula: Annual kWh ÷ (365 × peak sun hours × panel wattage × 0.8 efficiency) = panels needed.
What is the federal solar tax credit (ITC) and how much can I save?
The Investment Tax Credit (ITC) lets you deduct 30% of solar installation costs from federal taxes through 2032. For a $20,000 system, that's $6,000 back. It applies to equipment, labor, permits, and batteries. The credit drops to 26% in 2033 and 22% in 2034. State incentives can add 10-25% more savings.
How long does it take for solar panels to pay for themselves?
Typical payback period is 6-10 years in the US, depending on electricity rates, sunlight, and incentives. High-rate areas like California (20¢/kWh) see 5-7 year payback. Lower-rate areas (10¢/kWh) take 9-12 years. After payback, you're generating free electricity for 15-20+ more years.
How much can I save with solar panels over 25 years?
A typical 8 kW system saves $25,000-$50,000 over 25 years, depending on electricity rates and rate increases (historically 2-3%/year). Example: At $0.15/kWh producing 11,000 kWh/year, you save $1,650/year initially, growing to $2,500+/year by year 25 due to rate increases.
What affects solar panel efficiency and output?
Key factors: 1) Sun hours (4-6 peak hours ideal), 2) Roof orientation (south-facing best in Northern Hemisphere), 3) Shading from trees/buildings, 4) Panel tilt (latitude angle optimal), 5) Temperature (panels lose ~0.4% efficiency per °C above 25°C), 6) Panel degradation (~0.5%/year). Modern panels are 18-22% efficient.