Solar panels convert sunlight to electricity, without noise or pollution or fossil fuels. It's clean, renewable, and never runs out of fuel. The problem is that solar panels aren't very efficient. They only work during the day, when the sky is clear, and even then, only 20 percent of the sunlight is converted to electricity. This means you need many solar panels. And the more electricity you use, the more solar panels you need.

Sunlight Must Hit the Solar Panels

The following formula is only an estimate, because amount of electricity depends on how much sunlight hits the solar panels. This amount is affected by many factors, such as the weather, the tilt of your roof, even shadows from trees and buildings. Any change in these factors will affect how many solar panels are needed for your home.

How Much Electricity Do You Use?

Determine your energy usage. Electricity usage is measured in kilowatt hours, or kWh. Your electric bill will tell you how much electricity you use during the month. If you can't find that information on your bill, ask your electric company. Your electricity use will vary depending on your lifestyle, the size of your family, the weather, the amount of insulation in your home and the size, age and efficiency of your appliances.

The Formula

Calculate how many square meters of solar panels you need: kWH per month / number of days in the month X 1.25 = square meters of solar panels.

Example

So if you used 1,000 kWh in June, you need 42 square meters of solar panels: 1000 / 30 X 1.25 = 41.67. (This is about 452 square feet.) Solar panels are usually 2 meters square, so 42 square meters would require 21 panels.

Source:

Get your power from the Sun

Resource:

The Complete Idiots' guide to Solar Power for your Home