August 18, 2023, 8:55 am | Read time: 8 minutes
Solar systems are not only available for rooftops or as balcony power plants but also for carports. What is behind the “solar carport” concept? Here’s what owners should know.
The roof of a carport also offers the possibility for a solar system. Two experts explain on myHOMEBOOK what to consider with a solar carport: Stefan Hoffmann, an energy expert from the Consumer Center of North Rhine-Westphalia, and Harald Baumeister, founder and CEO of Sopago, a company that manufactures solar parking lot canopies.
Is every carport suitable for a PV system?
No, says Stefan Hoffmann from the Consumer Center. Shading from your own house or a neighbor’s can prevent effective use. Carports are also not designed to support larger loads like PV modules. “Therefore, it’s important to build a carport that is designed from the start to be used as a PV carport,” emphasizes Harald Baumeister, adding: “In the private sector, there are more freedoms with such carport PVs than with installations in public areas,” such as company parking lots.
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What needs to be checked before installation?
Important factors include the feasibility of obtaining permits, potential electricity yield, and the load-bearing capacity of the ground. “A building permit is always required for a PV carport in public spaces,” emphasizes expert Baumeister. It’s worth approaching the local building authority early, as regulations vary between municipalities and states.
Additionally, you must request a grid check from the local network operator for electricity feed-in. The electricity yield depends on potential shading from buildings and trees and can be calculated by us.
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South-facing should be perfect, right?
Not necessarily, says Hoffmann. The west-east orientation yields about 20 percent less output but has higher self-consumption. A gable roof with a 10 percent slope is very flexible; it can be positioned in all directions, and the yield is more consistent throughout the day than with a south-facing orientation.
Is the PV system a “separate” roof for the carport?
There are PV systems that can be mounted on existing roofs, depending on the construction. However, it’s crucial to check the structural integrity (including the snow zone). In Germany, there are different “snow zones” with maximum snow loads. This means: In Freiburg, less snow typically falls than in the Alps, which must be considered.
Retrofitting is always more complex than building a carport with a PV system from the start. Solar roof expert Baumeister says: “From planning, permitting, and proper structural design to construction, wiring, and connection, to financing, there are many synergies here.”
Energy expert Hoffmann explains: Both are possible. “If the PV modules are to be the roof, they must be approved as a building component. Currently, very few modules in Germany meet this requirement.”
Is there a maximum weight for such a system?
The structural integrity sets the limit, explains Consumer Center advisor Hoffmann. A standard module weighs 20 to 25 kilograms. Solar expert Baumeister points out that the weight also depends on the ground conditions and the foundation of the system. Additionally, in public areas, the maximum impact load from vehicles must be considered. This means: If a car hits the supports at a maximum of 10 kilometers per hour, the carport, such as on a company premises, must not collapse.
Do the modules differ from those on house roofs?
In principle, no, say Baumeister and Hoffmann. “Unless the modules are to form the roof,” explains the Consumer Center expert. Bifacial (double-sided) glass-glass modules, which generate electricity on both sides and are partially transparent, are suitable for carports. “However, these are not suitable for house roofs,” explains PV expert Baumeister.
Are there ready-made solutions, i.e., carports with integrated PV systems?
Yes, they exist, but currently mainly for the commercial sector. Manufacturers are now expanding the concept to private homeowners.
What should be considered during installation?
“Since this is a complex system that generates electricity, I strongly advise against installation without expertise,” says Baumeister. An electrician must be involved for the connection, as this is legally required. And they will be reluctant to sign off on a system they did not install themselves.
Expert Hoffmann points out an important aspect when choosing the plug through which the electricity comes from the roof into the house: “Few network operators allow Schuko plugs; most require the Wieland plug.” Carport PV system owners should inform themselves early with the respective network operator.
How much electricity does a solar carport provide?
It depends on the quality of the solar modules and their orientation to the sun. There are solar carports that deliver an average of 3.5 to 4 kilowatts peak per parking space, or 250 watts peak per square meter. The requirement for 1 kilowatt of power is about 5 square meters of space, explains Hoffmann from the Consumer Center. “The yield varies depending on the orientation,” he adds.
Can such a PV system be too large? Is there a risk of overheating?
Overheating is not dependent on the size of the system. The cables and inverters must be sized for the system, emphasizes solar expert Baumeister. “Especially with PV carports, we have the distance to the ground and thus better cooling of the system.”
Expert Hoffmann also rules out overheating. “The modules and inverters must be matched,” he says. “A PV system can be too large for economic reasons: if, for example, a lot is fed in but little is consumed.”
Can the PV system be directly connected to the household grid?
It is not connected but “plugged in,” says Hoffmann. If it is a plug-in PV system, the device can be “connected” via an outlet. A larger PV system is permanently integrated into the house grid by an electrical specialist.
Expert Baumeister explains: “The connection to the household grid is made with its own meter via the inverter. A storage module can also be integrated, so that part of the self-generated solar power is still available for the household at night, avoiding the need to rely on the supplier when the PV system is not producing.”
How does this connection work?
The direct current generated in the PV system is converted into alternating current in the inverter and fed into the power grid through a meter in the house. The generated electricity is always used first where the consumer is nearby, such as in the building, at the charging station, or in the battery buffer. The remaining, unused electricity is fed into the local power grid. This is currently the most economical solution for PV system operators.
Do you need an inverter?
“Yes, an inverter is always needed because the PV system generates direct current,” says Baumeister. To feed into the grid, whether house or public, it must be converted into alternating current. Additionally, this device controls and monitors the entire system.
Can you directly charge an electric car or e-bike?
To charge electric cars or e-bikes, you need wall boxes. These are supplied with electricity from the house connection. It is always the self-produced PV electricity, and only then is electricity drawn from the grid.
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Are carport solar roofs more prone to damage than PV systems on house roofs?
Stefan Hoffmann is not aware of any damage. Expert Baumeister also dispels fears. “If the requirements for foundations and wind or snow loads are statically considered, there are no more damages with PV carports than with roofs.” PV carports are statically tested and designed for specific maximum loads. Impact loads, wind loads, earthquake zones, and snow zones are also considered.
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What does a PV system on the carport cost?
There are now countless providers of solar carports. Baumeister advises: “It’s important to choose only providers that meet the German legal requirements for structural integrity, impact loads, and protection against falling glass.” Budget providers offer private PV carports with two parking spaces for under 10,000 euros. “Reputable manufacturers start at 20,000 euros for the material of a two-space PV carport, and 30,000 euros for turnkey solutions, including foundation, installation, and electrical connection.”
Hoffmann from the Consumer Center estimates turnkey PV systems on house roofs at between 1,500 and 2,500 euros per kilowatt peak (Kwp), depending on size. “Since installation on a carport may be simpler, prices could be lower.”