Updated: Aug 23
The number of solar panels needed to generate 30kWh per day or we can 900kWh per month depends upon many factors, like…
Peak sun hours of the state,
Facing of the rooftop,
Incline angle of the rooftop,
Shadowing on solar panels,
Wattage of the solar panels,
However, the size of the solar system that can be installed on your property is also subject to the space available to you. For example, a 35 kW of solar system can’t be installed on a 2,000-square-foot house. Many people can’t understand the space required for the installation of solar panels.
Moreover, without a proper solar survey, it is hard to say how much solar you required and how much can be installed. I recommend you take a solar survey to find the true potential of your rooftop.
Furthermore, considering some assumptions we can calculate how many solar panels are needed for 30 kWh per day (900 kWh per month).
How many solar panels for 30kWH per day (900 per month) in the USA?
To generate 30 kWh per day (900 kWh per month) from solar panels put on a shadow-free, south-facing rooftop in the United States, you will need 17 number of 400-watt solar panels for the state with 5-6 peak sun hours. In comparison, the same rooftop would require 28 numbers of solar panels (400 watts) to provide the same amount of power.
Peak Sun Hours: Peak solar hours are distinct from daylight hours. Peak solar hours are the times of day when the intensity of sunlight is highest. In other words, solar panels generate the majority of power during peak sun hours.
This means that, in comparison to states like Texas and California, where the average peak sun hours are the highest in the country, if you live in states like Michigan and Wisconsin where the daily peak sun hours is 3.5–4 hours, you will need 63% more solar panels to generate 30kWh per day (or 9000 kWh per month).
You can now see on the map below how much energy a 1 kW solar system can produce each day in every state of the USA.
With the help of the above MAP, you can calculate how many solar panels are needed to generate any amount of power or you can do a reverse calculation to find out how much power any number of solar panels can generate in any state of the USA.
Example: Solar panels installed in states with 4.5-5 peak sun hours, can generate 4.5 kWh per 1 kW, hence to generate 30 kWh per day you will require (30/4.5=) 6.7kW solar system or we can say (6700/400 =) 17 numbers of 400-watt solar panels.
Similarly, for a state with 3.5-4 peak sun hours, you will need (30/2.8 =) 11kW of the solar system consisting (11,000/400 =) 28 numbers of 400-watt solar panels.
By using the same method you can calculate, how many solar panels are needed for
Or you can do a reverse calculation to calculate how much power can the solar system generate in your city.
Size of solar panel: In order to calculate the number of solar panels you need, we advise choosing a higher-rated solar panel, such as a 400-watt model. This is because a 400-watt solar panel is only 28% larger than a 250-watt solar panel, but it produces 60% more electricity.
Are required for Solar panels: In addition, 400-watt solar panels are 22.75 square feet in size, and putting 16 numbers of them will cover 364 square feet of rooftop area. Furthermore, installing 28 of them will cover 637 square feet. Installing, such numbers of solar panels, required lots of skills, experience and tools.
Additional items for solar installation: In addition to solar panels, you will also require a solar inverter, AC/DC cables, AC/DC junction boxes, DC isolators and other pieces of equipment. Moreover, if there is any vent pipe on the south face of your rooftop, you will need to replace it to make space for solar panels. But, you don’t need to do that on your own, your solar installation company will do that for you with some extra charge.
Choosing the right solar company: A right solar company must have all the credentials required for installing solar systems, have expertise and credibility for installing solar equipment and be knowledgeable about all aspects of the process. A good rule of thumb is to work with installers who have at least three years of experience.
When you hire a solar contractor, one of the first things they should do is inspect your roof. Inquire with your installer whether they recommend roof repair prior to installation. Also, make sure you understand who is responsible for any roof damage or leaks that may occur.
Factors that affect the power generation of solar panels.
Facing of rooftop: In the United States, a south-facing solar panel generates the highest amount of power. This is because the United States is located in the Northern Hemisphere of the Earth, and the SUN is always in the southern portion of the sky in the Northern Hemisphere.
Furthermore, if you do not have south facing rooftop that does not means that you cannot install solar panels, this means you might need a slightly larger size of solar system.
Shadowing on Solar panels: Solar panels (or cells of a solar panel) that received lower sunlight than the rest, acted as loads and caused a drop in current, power and efficiency.
Hence, a shadow-free space on the rooftop must be determined before installation.
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 install solar panels there too.
Incline angle of rooftop: the rooftop incline angle also affects the power generation of solar power plants. In comparison to solar systems put on rooftops with a 20–30 degree inclination, those with a greater incline angle produce less power.
How much do solar panels cost for 30 kWh per day (or 900 per month) in the USA?
After factoring in the federal solar tax credit, the cost of installing solar panels for 30kWh per day or we can say 900kWh per month in the United States ranges from $14,280 to $20,060. Considering 16 numbers of 400-watt solar panels.
However, other factors can affect the cost of installing a solar system on your property. Like Rooftop construction: Solar installation firms charge based on the difficulty of the installation, and a complicated rooftop structure may increase the cost of solar installation.
Some extra work, like replacing the vent pipe and repairing the rooftop prior to installation will also increase the cost of your solar installation.
Type of solar panels: Solar panels are classified into two types: monocrystalline and polycrystalline. Monocrystalline solar panels are more expensive than polycrystalline panels. Monocrystalline, on the other hand, is more efficient and smaller.
Monocrystalline panels are preferable for rooftops with smaller shadow-free areas.
However, having a solar supplier that provides transparency, a courteous customer care team, and a well-established installation procedure makes converting to solar more accessible and approachable.