To determine how many solar panels you need to run a home, you first must understand how much energy you use during the average week. You can find out by looking into the energy bills that you receive monthly and calculate the average energy usage per day.

There are also other ways to determine your energy usage. For example, if you use 50 light bulbs for one hour, which are all 20 watts, this will consume 1 kilowatt-hour of energy. Expand this math to all your appliances and devices, and you will be able to calculate how much energy you use on average.

After understanding the average usage per week, your contractor can help you choose the best possible solution for your home by determining the surface area of your roof and how many panels can fit on your roof. But there are a few other factors that are impossible to take into consideration, such as overcast weather and outliers in your energy usage.

According to Solar.com, an average solar panel array of 400 square feet can produce anywhere from 300 to 850-kilowatt hours of energy per month. Depending on your energy usage, 400 square feet of panels may be enough, but it is best to consult your solar contractor. For example, a home in New York will generate less energy throughout the day than a home located in California because of the weather conditions and power of the sun.

An array of 40 panels, on average, produces around 14,000 kWh of energy, so depending on your energy usage and location of your home, you may need to increase the number of panels. There are even a few websites that allow you to calculate the number of solar panels that may be required to be fitted to your home. All you will need is your average monthly energy usage and what percent of energy from the grid you would like to offset with solar.

There are also a few other key factors to weigh, such as the surrounding trees and angle of your roof. These may seem non-essential to some, but these can put a significant dent in the amount of light consumed by your panels. Just an hour or two of shade during the brightest times of the day can put a considerable dent in the number of kilowatt-hours generated.

Another is the climate you reside in. All these instances mentioned may cause you to need a broader array of panels to generate enough power for your home.

One of the last things to consider is the efficiency of the solar cells inside the panels. Some panels are much more efficient than others. When determining which panels to invest in, it is best to take this into consideration.

Your solar contractor will be able to calculate the average amount of energy that can be generated from your solar panel array, along with the average consumption. These estimations are never exact because of changes in your usage and differences in the weather.