According to the U.S. Department of Energy (DOE), a standard 60-cell solar panel for home use measures around 39 inches by 66 inches. This works out to around 17.9 square feet per panel. Higher efficiency panels could generate more power without taking up much more space, and larger panels would take up more space but generate more power.
As a homeowner, the more important consideration is going to be how much space you have on your roof for solar panels. Your roof might have obstructions like chimneys or vents, skylights, and dormers. It will also matter how your roof is oriented and whether it faces north, south, east or west and what condition it is in.
According to the New Jersey Clean Energy Program, a home owner should consider how much usable roof space there is and its orientation before getting solar panels installed. It is also a good idea to get an evaluation of your roof and its condition to see if it is suitable for solar panel installation.
How Big Is a Solar Panel?
Solar panels come in a variety of sizes and shapes depending on the manufacturer and the wattage and voltage of the panels.
The New Jersey Clean Energy Program states that solar panels measure 39 by 66 inches on average for a 60-cell panel, or 17.9 square feet. The U.S. Department of Energy adds that 72-cells panels measure around 39 by 77 inches, making them 20.8 square feet.
Modern residential solar panels often utilize different configurations, so your installer should be able to give you exact dimensions based on whatever equipment they recommend. Also, the actual size of the panel does not indicate how much power it can produce. Two solar panels of a similar size could have greatly differing outputs.
How Much Space Does a Solar Panel Installation Take Up?
The overall size of a solar panel installation depends on how many panels you end up using.
At 18 square feet per panel, a 10 panel installation would take up 180 square feet, a 20 panel system would require 360 square feet and 30 panels would take up 540 square feet. The problem is that these are just estimates based on the theoretical maximum output of a single panel.
Solar panels take up more space than just the sum of their footprint on the roof because they need to be spread out to allow for airflow and they also have to be installed in a manner that takes local building requirements into account.
Your roof is unlikely to have 100 percent usable space for solar panels due to the presence of features such as vents, skylights, and chimneys. Dormers and other roof projections or recesses also impact the amount of space available for solar panels. The overall layout of the roof also impacts how many solar panels can be installed on it.
A 1,000 square foot roof does not necessarily have 1,000 square feet of area available for panels.
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What Reduces the Amount of Available Space for Solar Panels?
Features commonly found on roofs can impact the usability of the space. For example, a chimney could cut the space on a roof in half. Vents and plumbing stacks could leave unusable gaps in between panels. Dormers and roof valleys could also limit the amount of panels that can be placed on a roof.
Shading from objects outside can also limit your solar potential even if you have plenty of space on the roof.
The orientation of the roof is also a factor, with New Jersey Clean Energy Program noting that south facing roofs are ideal, but east and west facing roofs also work. They also advise taking the age of the roof into account when having solar panels installed. Installing solar panels on a roof that is going to need replacing in the near future is a waste of time and resources.
What This Means
Usable roof space is the amount of area on your roof that is available for panels.
Panel efficiency also impacts how many you need to buy and install.
For instance, say you have two solar panels that are roughly the same size, but one has a significantly higher output due to a higher efficiency rating. You would need fewer of these higher output panels to generate the same amount of electricity.
Lucent Energy notes that they design residential solar installations based on the energy needs of the client and that they recommend high-efficiency residential solar panels.
This approach recognizes the limitations of a home and the importance of designing a system around the needs of the client.
How Much Space Does a 5 kW Solar System Take Up?
A 5 kW solar system can be built using different sizes of panels.
For instance, 400 watt panels will require about 13 panels to produce just over 5 kW of power, whereas a 300 watt panel will need around 17 panels to produce the same amount of power.
Using the 18 square feet per panel guideline, the 13 panel 400 watt system will need 234 square feet of space on the roof, while the 17 panel 300 watt system will require 306 square feet.
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How Much Space Does a 10 kW Solar System Take Up?
Using the same 400 watt panel example, a 10 kW system will need 25 panels to generate 10 kW of power. This works out to 450 square feet of roof space. Again, this is just a guideline figure that does not take into account the shape of the roof or the location of any obstructions.
A solar professional should be able to take the specifics of your roof into account and give you an estimate of how many panels you need to buy and install.
Can Solar Panels Fit on a Small Roof?
A small roof could still have enough room for a solar panel installation.
It is all about the total output required and the size of the panels you end up buying. Higher output panels reduce the number of panels you need to buy and install.
The energy needs of the home will depend on how much electricity the occupants use.
A household that uses a lot of electricity will require a larger system than one that uses less electricity.
Electric heating systems and air conditioning units, as well as electric vehicles and other appliances add to the overall electricity needs of the home. It is all about determining how much usable roof space you have that can support a solar panel array and whether that is enough to meet the needs of the home.
Do Solar Panels Require Extra Space Around Them?
Solar panels cannot just be placed on every square inch of your roof.
The installation has to be completed in such a way that it meets local building and electrical codes. It also has to take the physical properties of the roof into account. New Jersey Clean Energy Program notes that building permits and electrical permits are needed before hand and that homeowners should discuss these permits and their costs with the contractor. It is up to the installer to determine the best way to place the solar array on the roof in accordance with local requirements.
What If Your Roof Is Too Small for Solar Panels?
If you have a small roof, it does not mean that you cannot have solar panels installed.
An installer can look at your roof and see if there are other roof faces they could use. They can also advise you on the best way to orientate the solar panels to get the most out of them. In some cases, a ground mounted array could be considered as an alternative, but ground mounts arrays have their own set of requirements and considerations.
In New Jersey, there are additional environmental regulations that have to be taken into account for solar panel installations, especially those that are mounted on the ground. This is particularly the case for environmentally sensitive areas and the coast.
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What You Need to Know Before Getting Solar Panels Installed
To install solar panels, you need to know the number of panels, the size and shape of the panels and the usable roof space. The number of panels is determined by the system size. The size and shape is determined by the manufacturer. The usable roof space is determined by a site assessment conducted by a professional.
Using the 20 panel example again, if each panel measures 18 square feet, you will need around 360 square feet of usable roof space. Keep in mind that this is just a very rough estimate and that a professional installer will have to conduct a site assessment before they can come up with a more realistic number.
Why Professional Solar Panel Installation Is Important
Designing a solar panel system requires considering a number of different factors
including power production capabilities, the size and shape of the roof, shading, orientation, electrical and building requirements, and permits.
Lucent Energy works with residential clients and offers a complete service from energy analysis to permits and interconnections. They specialize in residential solar panel installations and work throughout New Jersey. When reviewing quotes from different solar companies make sure to compare the overall design and assumptions of the system, not just the number of panels.
In particular compare the total size of the system in kilowatts, the expected production in kilowatt hours, the specific solar panel type, roof sections, warranty and assumptions about production.
Also Read: How Do Solar Cells Generate Electricity?
Final Thoughts
A single residential solar panel measures around 18 square feet but the total roof space needed for a residential solar panel installation could range from a few hundred square feet to several thousand square feet, depending on the energy needs of the home and the solar panels that are purchased.
Usable roof space is a more important consideration than the overall size of the roof. Obstructions like chimneys and vents, skylights, dormers, shading, orientation, roof age, and roof shape can all impact the amount of solar panels that can be installed.
For a homeowner in New Jersey seeking to install solar panels, the best option is to obtain a professional evaluation of the roof to determine the system size and configuration. When identifying the best solar panel company in New Jersey it is important to compare the overall system design, including the equipment, size and expected production, rather than the number of panels.