May 3, 2018 Solar Energy Written by Greentumble Editorial Team
Ground mount vs roof mount
The main component of a photovoltaic (PV) system

are solar panels, not only due to their function of converting the sunlight into electricity but also because they are the popular visual reference of any PV system. But there is also other equipment that acts behind scenes and is crucial for any solar installation. We are talking about the mounting systems.

Mounting systems hold solar panels in place whether it is on the rooftop or on the ground. They also provide the structural strength needed to support the natural weight of the panels, the force of the wind and in some cases the weight of the snow.

There are two main types of mounting structures: the rooftop and the ground one. The decision to use one or another depends on several factors and will affect the overall investment cost of your solar project, while at the same time the installation time and procedure. So be very sure to choose the one that better fits your economical and technical needs.

Here we will discuss some of the features and types of mounting structures and list the advantages and disadvantages of each type.

 

Ground mounted solar panels

The typical mounting structure used for large commercial or utility projects is the ground mounted system. However, on the residential scale, ground mounted structures can be applied as well and might come with some great benefits that roof mounted cannot provide.

Ground mounted installations consist of a metal frame that is fastened or anchored to the ground to support the weight of solar panels.

How do you know if ground mounted systems suit your needs? Let’s have a look at their pros and cons to give you a better idea:
 

Advantages of ground mounted solar panels

Ground mounted solar system

Ground mounted solar system

Orientation and inclination variability

One of the biggest advantages of ground mounted solar systems is their maneuverability. You have several design options and you are free to decide on one that suits your needs better.

If the backyard faces South, West or Southwest the system will have a perfect location to perform the best. The tilt angle can be also directly adjusted to achieve maximum possible irradiance during the day. Even if the system does not face the South directly, you can easily tilt your panels to get the maximum possible sunlight.

Regarding the inclination, ground mounted panels often come with much better range to choose from, when compared to roof mounted panels, because their tilt depend highly on the roof inclination [1].
 

Easy maintenance

One of the main factors that needs to be considered when installing a solar system is the maintenance, especially if the location is in the Northern latitude.

Snow is a great enemy of solar efficiency. Therefore, maintenance and cleaning should be executed periodically during the winter season, not only to avoid electrical losses but to prevent blocks of ice from sticking to the panels.
 

Bigger system size

Ground mounted systems tend to be larger in size and in the power output. The space availability is usually larger than on the roof [2].
 

Higher performance

Due to the previously stated reasons, ground mounted systems have more design and positioning options, therefore, their power output, efficiency and performance can be better than of rooftop panels [1].
 

Safer electrical grounding system

Grounding resistance depends on factors such as the soil condition and the configuration selected by a designer.

In general, the more wire you use to conduct the current to the ground, the less effective the system is. But since ground mounted systems are already located on the ground the distance to reach the electrodes is way shorter.

So, this mounting system can protect your solar panels more effectively against any electrical fault or insulation failure.
 

Good cooling system

Solar panels efficiency is affected by the temperature changes. With higher temperatures, efficiency drops.

In warmer climates is necessary to have some cooling system that keeps panels within acceptable temperature range, especially during the summer.

The natural air flow in the ground mounted systems is the best and the most economically viable cooling system [1].
 

No modifications to the house structure are needed

One of the best features of ground mounted systems is that you do not need to make any changes to your roof or the facade of your house. This way you avoid possible damages to your roof (mainly due to bad installations procedures) [3].
 

Visual aesthetics is not a problem

Many people do not like the fact that solar panels are visible from the front door, actually some homeowner associations do not allow the presence of solar panels visible from the street.

You can prevent this problem with the ground mounted system, because solar panels will be placed in the backyard of your house [2].
 

Well suited for tracking systems

Installation of tracking systems in ground mounted structures is way much easier than it is for rooftop systems.
 

Expansion

Solar rooftop systems do not leave much space for expansion considerations, but if the space in your backyard is large enough, adding extra panels to your ground system is much easier and cost effective.
 
Now, What about the disadvantages of ground mounted systems?
 

Disadvantages of ground mounted solar panels

 

Higher installation costs

Ground mounted solar systems require additional structures and materials. The necessary foundations to install the system, the soil-structural analysis and labor, therefore, these systems tend to be more expensive than rooftop [2].
 

Land use

One disadvantage is that the backyard of your house will be occupied by the panels for the next 25 years. If your backyard is big enough that might not be such a problem, but in smaller yards, you may have only limited space for other recreational activities (barbecues, parties, gardening) left [4].
 

Safety

Given that the solar panels require electrical installations and are producing electricity during the day, many homeowners are afraid that if they have kids nearby they could touch the system and either damage it or put themselves in danger.

Most solar systems are carefully grounded and protected. Micro-inverters and wires should be well covered. However, it is possible that with time there could be some malfunction, insulation deterioration or damage caused by weather conditions or due to the bad design and installation. In cases like that wires could become exposed and pose a risk to other family members.

The key to avoid this problem is to make sure that your solar installer is certified and that the installation procedure follows the electrical code (this will be verified by the local utility company). You must also check your solar system for damage after any strong meteorological events.
 

Shading

Shading negatively affects efficiency of your solar panels. Ground mounted systems might be exposed to additional shading due to the presence of trees or structures that your neighbors might want to locate within their property.

Considering the long lifespan of solar panels, it is advisable in any case to not locate the solar system close to your neighbors’ property.
 

Installation speed

As the ground mounted systems require additional components and considerations, the installation usually takes longer than rooftop installation does [5].
 
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Roof mounted solar panels

Rooftop solar systems are the most popular setups for residential installations. This configuration allows you to install solar panels on the roof of your house by fastening panels to the rail system or to the flashings (if the system is rail-less).

The selection of the type of a roof mounted system varies depending on the cost of materials and the roof type, as some systems are not suited for all roof types.

There are advantages and disadvantages of these mounting systems that are worth analyzing when deciding to install a solar system in your household.
 

Advantages of roof mounted solar panels

Roof mounted solar system

Roof mounted solar system

Installation costs

Roof mounted systems tend to be less expensive than the ground mounted systems because the installation procedures require less labor and time to finish.

But there can be a limitation. If your roof needs to be upgraded in order to be able to resist the weight of the panels over the lifetime of the system, then the installation costs could rise higher.

Another consideration comes regarding the lifetime of your roofing material. If the roofing material needs to be replaced sometime in the close future, the overall cost of installing solar panels on your roof could exceed the estimated budget for the project [2].
 

Utilization of unused space

One of the best things about the rooftop mounted systems is that the solar panels will be installed in the space you do not use frequently, and therefore, they will not get in the way for any of your activities.
 

Easier and faster installation

It is widely accepted by solar installers that rooftop systems are generally easier to install than ground mounted systems. It is mainly because there are less components and tools needed to complete mounting and the task can be done with less installers, as there is no need to dig a foundation, which takes time and effort [4].
 

Protection of your roof surface

Although solar panels are not intended for such purpose, the placement of solar panels on your roof will protect the roofing against snow, strong winds and even from other objects [6].
 

Minimum shading

This advantage depends widely on the location and structures around your house. In general, solar panels placed on the highest part of the house have lower probability to be shaded by nearby trees or buildings, which at the end affect efficiency of your whole system.

Unless you have chimneys, antennas, vents or other objects on the roof that might cause self-shading.
 

Limited access to solar panels

One of the cons of ground mounted is the easy access of children or unauthorized persons to your solar system.

Placing your panels on the rooftop assures your kids will be absolutely safe and minimizes the probability of any intruder that might want to access your panels.
 

Orientation

The advantage applies if the orientation of the panels can be set to at least 2 to 4 different orientations (front door side, back side and lateral sides). This allows the designer to select the best orientation towards the South to achieve maximum solar irradiance.

If the roof only has one side suitable for the installation and it does not face South, then it becomes a limitation instead.
 

Aesthetics

This advantage is related to the availability of roof sides as well, because some homeowners do not like the appearance of solar panels on the front side of their house. It can be easily solved by placing the panels on the back side.

On the other hand, the presence of a photovoltaic system on the front side of your house might be viewed as a sign of being environmentally-friendly person.
 
Now what about the cons of the roof mounted system?
 

Disadvantages of roof mounted solar panels

 

Roof perforation

No matter what type of roof you have, it will be necessary to install the racking system or the support flashings with bolts to fasten your solar panels and that implies that your roof needs to be perforated.

The more hole perforations your roof has, the more chances for it to fail during the lifetime of the solar system [1].

Sometimes, the holes will need to be drilled during the measuring phase, therefore, you must make sure that the installer uses some sealant to protect your roof from incoming rain or other weather conditions [6].
 

Structure upgrades or reparations

It can happen that the roof of your house is not suited for solar panel installation, either because of structural damage or bad design.

If that is the case, you will need to replace, upgrade or repair your roof [1].
 

System size

The roof space (without chimneys or antennas) is usually much smaller than the available space on the ground. And since the area is directly related to the maximum power that can be obtained from your system, roof mounted systems have lower maximum power limit than ground mounted systems.

That means that you might not be able to suffice all your required electrical load needs. Instead you will have to consider based on the possible power output which electrical devices will represent the critical loads.

Limited roof space also minimizes the possibility of expansion and possible improvements in the future of the system.

This probably represents the main downside of rooftop mounted systems.
 

Maintenance

Maintenance is essential to assure good efficiency of solar panels. The roof mounted solar systems are less accessible and their maintenance is tougher, especially during the winter season when everything is slippery.

Using hoses or water pressure to clean panels is not a good idea either, as it could cause cracks in the glass and even cancel the warranty of the system.
 

Neighbor restrictions

Sometimes homeowner associations prohibit the residents of the area to install solar panels in visible areas from the street. If the front side of your house faces South, then this will be a problem.

Rooftop solar installation in the city

Rooftop solar installation in the city


 
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Conclusion

As you can see there are quite some criteria to consider when selecting the proper solar mounting system for your house. There is no recipe to tell you which one to choose, as there are several things to take into account and to discuss with your solar installer.

However, there are a few tips that might give you an idea.
 

When to choose roof mounted system?

You should select the rooftop option if…

  • The available space in the backyard is used for garden, barbecues or recreational purposes and there is no space for these activities and solar panels at the same time. Would you like to lose the chance of having fun in your backyard? I don’t think so.
  • Your roof has several sides available for solar panels.
  • Your rooftop is not made of Spanish shingles
  • You do not wish for any excavation or digging in your backyard
  • The only space available for solar panels in your backyard is very close to the neighbors’ property
  • Your house or roof are new or recently fortified
  • The available space on the roof is enough to cover your electrical needs
  • The installation costs of roof mounted are lower than ground mounted.

 

When to choose ground mounted systems?

You should select the ground option if…

  • Your space in the backyard is wide and extensive.
  • The available space on the rooftop is not enough to supply the electrical load that you need.
  • There are long hard winters or a lot of dust and sand in your location.
  • You think there might be space for some possible expansion of the system in the future.
  • Your roof is unsafe and after replacement costs would be more expensive than a ground mounted installation.
  • There are restrictions in your neighborhood regarding the installation of solar panels in the rooftop
  • The overall efficiency achieved by a ground mounted system will be higher than the roof mounted due to the tilt and inclination angles.
  • You wish to install a tracking system.
  • There are chimneys, antennas or vents in the rooftop that might cause shading.

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References

[1] https://www.altestore.com/blog/2012/07/top-six-reasons-to-do-a-ground-mount-vs-roof-mount/
[2] https://www.solarpowerauthority.com/ground-mounted-versus-rooftop-mounted-solar-panels/
[3] https://www.finder.com.au/benefits-of-ground-mounted-solar-panels
[4] https://www.spectrum.solar/uncategorized/ground-mounted-solar-vs-rooftop-solar/
[5] http://statkraftblp.com/ground-mounted-vs-roof-top-reality-check/
[6] https://www.youtube.com/watch?v=hkT2fVZ9C5g