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Solar Panel Calculator

Estimate how much electricity a rooftop solar system could generate, how much it could save and how long it might take to pay back.

How it works Report a problem

Solar Energy Calculator

Enter your values below and press Calculate to see your result instantly.

Annual Energy Production
9,125 kWh
Annual Savings
$1,368.75
Payback Period
10.9 Years
System Capacity 5.0 kW

About the Solar Panel Calculator

Estimate how much electricity a rooftop solar system could generate, how much it could save and how long it might take to pay back.

How to use the Solar Panel Calculator

  1. Enter your Available Roof Area (sq ft) and the daily Sunlight Hours.
  2. Choose the Panel Efficiency and enter your Electricity Rate ($/kWh) and Installation Cost.
  3. Press Calculate.

Formula and method

Peak power ≈ area (m²) × panel efficiency × 1 kW/m². Daily energy ≈ peak power × sunlight hours (before system losses). Savings = energy × electricity rate. Payback = installation cost ÷ yearly savings.

Worked example

300 sq ft (27.9 m²) of 20% panels with 5 sun hours gives about 5.6 kW peak and roughly 28 kWh a day before losses.

Tips

  • Shading, roof angle, dirt and inverter losses reduce real output by 15 to 25 percent.
  • Get quotes from local installers and check for incentives.

Frequently asked questions

How long do solar panels last?
Most come with warranties of 25 years and keep producing well beyond that, with a slow decline in output.