The number of solar panels needed to generate 100 kWh per day [or 3,000 kWh per month] is determined by your state’s weather conditions, the rating of the solar panels, and the condition of your rooftop. Moreover, the size of the solar system that can be installed on your rooftop is subject to the area and orientation of your rooftop.
Furthermore, the amount of power generated by solar panels varies with the weather throughout the year, also the amount of power required to run the house varies too so you need to be clear whether you need solar panels to generate 100kWh of power per day for any particular month or on average.
Take a solar survey to find true potential of your rooftop.
However, some other factors will affect the power generation of solar panels, such as rooftop facing, shadow-free areas, and peak sun hours in your city. As a result, to calculate the number of solar panels necessary to generate 100 kWh per day or 3,000 per kWh per month you need to know a few things.
First, we are assuming you need a solar system to produce 100 kWh on average in a year. Otherwise, it will be a little bit complicated to calculate the number of solar panels.
Second, it is recommended to go with a higher-rated solar panel like a 400-watt, because a 400-watt solar panel is only 28% bigger than a 250-watt solar panel. However, it generates 60% higher power than a 250-watt solar panel. Going with a higher-rated solar panel is both space-saving and economical.
Third, we are assuming that you have a south-facing rooftop because in the USA a south-facing solar panel generates the highest amount of power. This is because the USA is located in the Northern Hemisphere of the earth and in Northern Hemisphere; the SUN is always along the southern part of the sky.
However, if you do not have a south-facing rooftop that does not mean that you can't install solar panels that means you might need a slightly larger size of the solar system.
Fourth, we are also assuming that you have a shadow-free rooftop, because solar panels (or cells of a solar panel) that received lower sunlight than the rest, acted as loads and caused drops in current, power, and efficiency.
However, if your rooftop (or part of the rooftop) has some shadow for a short period, then you do not need to worry, you can still install solar panels there.