How Many Solar Panels Can I Fit On My Roof? (9 Factors & Computation) is reader-supported. When you buy something through links on our site, we may earn an affiliate commission.

The growing intent of environment friendliness has made solar panels a piece of standard equipment for every other household in the United States. Solar Panels harness solar energy to produce electricity for your home and business. 

How many solar panels can I fit on my roof? It depends on several factors. An average-sized house in the United States can hold a maximum of 97 solar panels, and these solar panels work together to produce 31 kW (kilowatts) electricity. Though the average roof size can accommodate so many panels, you need to determine your electricity needs and install them appropriately.

Several factors need to be considered for determining the number of solar panels you need to install. Sometimes, you might need more electricity than what the roof can accommodate. What do you do in that case? Let us discuss everything in detail in this article. Shall we get started?

Factors Determining How Many Solar Panels can you install

To determine how many solar panels you can install, several factors must be considered, and let us look at each of them in detail.

1. Size Of Your Roof

The roof size is the most prominent and essential factor in determining the number of panels to be installed. For this, you need to compute the size of your roof and the average size of the panel to decide how much the roof can hold. Also, do not forget to assess your energy needs. If the roof cannot accommodate the panels to produce the required energy, you need to compliment the roof energy with additional facilities.

2. Roof Requirements

The roof must assist the installation of the solar panels in a 40-degree pitch without any shade. Check if your roof suits you well. If not, you need to find another way to meet your energy needs. You may probably think about purchasing high-end efficient solar panels.

3. Roof Orientation

Roof Orientation refers to the position of the roof relative to the sun. You need to measure the area your roof can accommodate based on the roof orientation. If you want the panels to be installed on the southeast side of your roof, you can measure the length of the roof along this side and the east side of the corner where the roof ends.

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Do you know why you should measure the wall instead of the roof area? You cannot climb up the roof and measure the area of the roof. Measuring the wall might be a safer option though it is a rough measure.

4. Orientation and Shading

Your roof orientation is critical in determining how many panels you need to install to get the required energy. You should place your panels in the south, south-east, or south-west side of the roof. If your roof does not accommodate the panels in any of the said directions, it is likely ineffective.

Shading also plays a crucial role. If your roof has a shady area or a chimney that casts a shadow on the roof, inevitably, the panels cannot produce the optimum energy. Make sure you position the panels away from the shades.

5. Size of the Solar Panels

The average size of a solar panel is 78.74 X 157.48 Cms. You can use this measurement to compute the total area required to install them and the number of solar panels required. But, in reality, the measurement of each panel may vary between different brands. 

Pay attention to the brand’s measurements that you choose and compute the required panels accordingly. 

6. Budget

While the size of the roof and the panels are essential factors to consider, budget plays a crucial role. While you get to save the extra penny from the electricity utility bills, solar panels involve hefty upfront investment and installation costs.

7. Energy and Usage Production

You need to determine how much energy the solar panels can produce after ascertaining the roof capacity. You should also arrive at the average power that you may consume. This comes to a point where, with the given roof capacity, the number of solar panels installed, the required energy, and the energy produced by the panels, whether you will end up having excess or deficit energy.

8. Peak Sun Hours

The Peak sun hours are the total number of hours during which the intensity of the sunlight would be at the maximum. This is called the good moments of the day, where the panels make optimum production.

The peak sun hours in your area determine the number of solar panels that you would require to meet the energy needs. For example, in California, the peak sun hours come to 5 to 7.5 hours daily. Multiply the total peak sun hours by thirty. This will give you the total peak sun hours for the month. You can then arrive at the total kilowatt-hours your panels can produce during peak sun hours. 

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9. Time Spent at Your Home

Can you believe that the time you spend at your home is also an essential factor to be considered while deciding upon how many solar panels to install? Yes. 

If you are at home, you can purchase more extensive panels. The more efficient panels can produce more energy which caters to the entire household requirements. 

If you are at home only during the night, the energy generated during the day gets stored in the battery, and you get to use only a small portion of it. And if you are attached to a grid system, the energy you produce goes directly to the grid, and you will be paid for the excess energy sent to the grid.

But, the amount saved on the electricity bills is higher than the amount received from the grid. So, if you are not going to spend the entire day at home, you can choose a smaller panel and save on the initial investment.

How to Compute the Roof Space?

You need to compute the roof space for determining how many solar panels the roof can accommodate. The following steps explain how to calculate your roof space.

Step 1

The first step is taking three critical measurements of the roof.

  • Height of the highest point of the roof to the Joints (A)
  • Distance of the joint from the horizontal apex till the roof`s eaves (B)
  • Length of the roof`s peak (C )

Step 2

Once you have all the three measurements ready, workout the following formula,

A^2 + B^2 = X^2

X is the distance between the apex and the edge of your roof.

Step 3

In this step, you need to use the value of X obtained in step 2 to compute the roof area.

Area of Roof = C x X 

The roof area is the total area available to accommodate the solar panels to be installed. In general, it is recommended to deduct 30 Cms from the result of the above computation, and this is done to ensure that you don’t include the roof’s edge where the solar panels cannot be installed.

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How do you make space for additional solar power?

After determining the house’s energy needs, if your roof space cannot accommodate enough solar panels to support it, you can choose either of the two options.

  • Reduce the energy needs by switching to a more energy efficient lifestyle, choosing better point-consuming equipment, and not wasting much energy.
  • If you are hesitant about making the lifestyle change, you can simply mount your panels on the ground instead of the roof. While this has its pros and cons, it can at least cater to the energy requirements.

What is the average number of solar panels required based on the size of the panel system?

Based on the size of the system and the maximum power that the solar system can produce, the following table depicts the number of solar panels required.

System Size (kW)Estimated Monthly Energy Production (In kWh)Number of PanelsRequired Roof Space (In Sq Feet)
480 – 60012220

Note: The number of panels has been determined based on the assumption of 320 Watt solar panels.

Take Away

It is choosing and installing solar panels, which is very tough for us to decide. Several factors influence how many solar panels are required for you, and some aspects like Orientation, shading, and roof requirements are hard to quantify.

To make things easier, you may take the services of the professional team. You can get competitive quotes from various professional experts who do the job for you. They would also give you the energy requirements, the roof size, required panel sizes, and the upfront costs required. They also give you an insight into the rebates, incentives, and tax benefits that you will be eligible for based on your local laws.

If you prefer the other way, we have enriched you about the various factors and methods to determine the size of the panels and roof—all the very best.