Estimate the amount of solar panels needed to satisfy the electrical power usage of your home by dividing your average daily energy use by the amount of solar resource available to your region and multiplying that number to adjust it for the efficiency of your panel. Gather your utility bills, and by using a computer, it takes about 30 minutes to calculate the amount of solar panels you need.
- Determine the electrical needs of your household
Start by assessing your home's average annual energy consumption rate. Gather your utility bills, and compare more than just one year's worth of data for accuracy. Divide that figure by 365 to get an average daily amount in kilowatt hours.
- Consult the National Renewable Energy Laboratory for the amount of solar radiation that your area receives
Visit the National Renewable Energy Laboratory's website, and click on the blue highlighted text next to "Photovaltics Data - 1998 to 2009 Low Resolution (letter size)," to find the average amount of solar insolation available for your area in kilowatt hours per meter squared per day.
- Calculate your home's energy requirements
Divide your daily kilowatt hour needs by the kilowatt hours available.
- Adjust your calculation for the efficiency of your solar panels
Average panels only utilize 15 percent of the sun's rays. Multiply your number by 6.625 if your panel is 15 percent efficient and 4.75 if your panel is 21 percent efficient to determine the total number of square meters needed. Multiply the meters by 3.2808 to get feet.