Now that you know how much solar radiation is available and how much of it can actually be utilized by a solar panel, you can calculate how many photovoltaic solar panels you will need in order to replace your current source of electricity. You will need to find out the exact size of each cell in square meters, as well, which can probably be found on the website of, or in literature from, your manufacturer of choice.
If we assume an average energy usage of 1000 kWh per month, we will calculate: “Solar radiation” x “Surface area of the panels in m² ” x “0.07” (7% Estimated solar panel efficiency) x “Average days per month” (365/12). We will then divide that number into 1000 (The average energy usage of 1000 kWh per month).
For example, in an area with solar radiation of 5 kWh/m²/day, with a solar panel of 2 m², the equation would be:
5 (Solar Radiation) x 2 (Surface Area of standard solar panels) x 0.07 (Solar Panel Efficiency) x 30.42 (Average n° of days per month) = 21.294 kWh produced per panel each month.
To cover at 100% the month Kw usage of 1000Kw divide 1,000/21.294 = 47, so you would need 47 m² of panels to completely eliminate your electricity bill. (Here a more detailed description of how many 80W solar panels are needed to power a home)