Free Tool — Solar Energy
Solar Panel Calculator 2025
Enter your monthly electricity bill and state to instantly find out how many solar panels you need, your estimated system cost, and how long until you break even.
Your Information
How the Solar Calculator Works
Step 1: Energy Usage
We divide your monthly bill by your state's average electricity rate ($/kWh) to estimate your monthly and annual kWh consumption.
Step 2: Panel Count
Each 400W panel produces about peak sun hours × 0.4 kW × 0.8 × 365 kWh/year. We divide your annual usage by this figure to get the panel count needed.
Step 3: Cost & ROI
System cost is estimated at $3/watt installed. The 30% federal ITC is applied automatically. Payback = net cost ÷ annual savings.
Frequently Asked Questions
How many solar panels does the average home need?
The average U.S. home uses about 10,500 kWh per year and needs 20–25 solar panels (400W each) for a 6–10 kW system. Homes with a $150/month bill in a sunny state typically need 15–20 panels.
What is the average solar panel payback period?
The national average solar payback period is 7–10 years after the 30% federal ITC. In high-electricity-rate states like California, Massachusetts, and Hawaii, payback can be as short as 5–7 years.
How much does a solar system cost in 2025?
A typical 6–10 kW residential solar system costs $18,000–$30,000 before incentives in 2025. After the 30% federal Investment Tax Credit (ITC), the net cost is typically $12,600–$21,000. State incentives can reduce costs further.