Solar Panel ROI Calculator

Step 1: System & Financial Inputs

All data stays in your browser. Nothing is sent to our servers.

Step 2: Your Solar ROI Results

Step 3: History & Comparison

How It Works

This 25-year financial model simulates the real-world economics of rooftop solar. Here is the calculation logic:

1. Gross cost: System size (kW) × 1,000 × cost per watt = total installed price before incentives.
2. Net cost: Gross cost minus federal tax credit and any state rebate you enter.
3. Annual production: System size × daily solar resource (kWh/m²/day) × 365 days × 0.75 system-loss factor. Degradation is modeled at 0.5% per year.
4. Self-consumption vs. export: Production up to your annual usage is valued at the full retail rate. Excess production is credited at the net-metering rate you select.
5. Escalation: Utility rates rise by your chosen annual percentage, which increases the value of every kilowatt-hour you avoid buying.
6. Payback: The year when cumulative savings exceed the net system cost. If it never happens within 25 years, we report '>25'.

Tip: Use the Home Energy Bill Breakdown tool first to get your accurate annual usage. Oversizing solar relative to usage wastes money.