Solar panels use racking systems with several mounting options, and they can be used on most residential roofs. However, even if you have an adequate roof, finding the optimal orientation and layout for your panels is also very important. Ideally, you will want to use the roof areas with the most sunshine, while avoiding shaded areas as much as possible – even a small shadow can greatly reduce the energy output of your solar array.
Installing solar panels is relatively easy if you have conventional asphalt shingles or a standing seam metal roof.
On the other hand, some roof tiles may be damaged if your roof uses a brittle material like slate or clay. However, if you work with professional solar installers, the number of broken tiles will be minimal or zero.
Asbestos is the only roofing material that may limit your ability to add solar panels as most providers will not work on these roofs. Harmful fibers are released when manipulating asbestos, especially when drilling. These fibers are not only dangerous for the installers, but also for anyone living under that roof. If this is your situation and you plan to go solar, a complete and well-planned roof replacement is strongly recommended.
What Is the Ideal Roof Orientation and Pitch for Solar Panels?
Generally, the area required for a typical PV solar panel system will be smaller than your total roof area. Consider that each solar panel requires around 18 square feet of roof space, and you will normally need three panels for each kilowatt of capacity. If you plan to install a 6kW system, this is equivalent to roughly 18 panels and 324 sq.ft.
Even if the roof space is abundant, your solar panels will generate more electricity when using the sunniest part of your roof. This translates into increased savings on your home energy bill, a quicker payback period, and a higher return on investment.
- If you live in a northern hemisphere country like the US, south-facing roof sections will get the most sunshine – unless there’s a large object like a tree or a neighboring building casting a shadow. This happens because there is more sunlight coming from the south due to your geographic location.
- Since the sun rises in the east and sets in the west, east-facing solar panels are more productive in the morning, while west-facing panels are more productive in the afternoon.
- Finally, north-facing solar panels are the least productive throughout the year, since there is less sunshine coming from that part of the sky.
In southern hemisphere countries like Australia, the effect of north and south orientations is the opposite: solar panels are more productive on north-facing roofs, and less productive on south-facing roofs.
If you want to maximize the kilowatt-hours produced by solar panels, they should be installed in south-facing areas of your roof. However, you should also consider your consumption habits and electricity tariffs:
- Homes tend to have a higher energy consumption in the afternoon and evening.
- Many electricity providers charge higher kilowatt-hour prices during peak demand hours.
- In other words, electricity tends to be more expensive when homes need it the most.
Did you know? In some homes, a west-facing solar array may achieve greater savings than a south-facing array. The electricity output in kilowatt-hours may be slightly less, but you will be reducing your grid consumption when kilowatt-hour prices are higher.
The roof pitch also affects the productivity of solar panels, but not as much as orientation. As you move further to the north, the sun’s position in the sky is lower, and the ideal tilt angle for solar panels is higher.
For example, the ideal tilt for solar panels in Miami FL is 25° facing south, but the ideal tilt increases to 42° in Portland OR, located farther to the north.
Solar panels are easier to install if they use the same pitch angle as your roof. Otherwise, you need a more complex and expensive racking system. If your roof has multiple pitches, you can use the sections that are closer to the ideal tilt angle for your location.
A qualified solar provider will use a solar system design software to simulate the performance of the solar panels, finding the optimal orientation and layout based on your roof design.
Can My Roof Support the Weight of Solar Panels?
Other than roof orientation and pitch, structural capacity is another important factor to consider before installing solar panels.
- The exact weight will depend on the specific brand and model, but residential solar panels normally weigh between 40 and 50 pounds.
- For a 6kW system with 18 solar panels, you would be adding around 720 – 900 pounds of weight to your roof – plus the weight of mounting equipment.
A qualified solar provider will conduct a structural assessment of your roof before proceeding with the installation. If you need a roof upgrade before installing solar panels, they will make it clear right away.
Regardless of the material used, if your roof is very old you should consider a replacement before installing a solar power system. Keep in mind that solar panels come with manufacturer warranties of up to 25-30 years, but they are subject to several conditions. If solar panels are installed on a roof near the end of its service life, and you must remove them for a roof replacement, the warranty may be voided.
Are Solar Panels Affected by Roof Shading?
Solar panels are very durable, and they offer an excellent ROI when used in a suitable location. However, shadows can drastically reduce their output, and should be avoided as much as possible. Due to how solar panels are connected, a single shaded module is detrimental for the entire array:
- Solar panels are connected in series circuits, or strings.
- If you cast a shadow over one panel, the effect is similar to closing a valve on a pipe.
- Even if all other panels in the string are getting enough sunshine, they will be less productive because the shaded panel restricts current.
Since the sun’s position changes depending on the hour and season, shadows are constantly moving. However, solar design software can simulate shadows during the entire year, and the best solar providers will use this feature to find the optimal layout.
Also, keep in mind that roof shading can change over time due to the growth of trees and new constructions. However, many states have solar easement laws to prevent constructions that would cast shadows on roofs with photovoltaic panels. Roof shading caused by trees can be prevented with regular pruning and trimming.
Which Roofing Materials Are Suitable for Solar Panels?
In general, if your roof is relatively new and in good condition, solar panels can be installed over almost any material – except for asbestos due to the health hazards involved. However, some materials make solar installations easier, while others require additional steps.
In the following table, we will summarize key aspects to consider before using solar panels on some of the most common roofing materials:
|Roofing Material||Is my roof suitable for solar panels?|
|Asphalt shingles||Yes, solar panels can be installed with a standard penetrating mount. Keep in mind that asphalt roofs tend to last between 15 and 25 years, while high-end solar panels are warrantied to last for 25 years or longer.|
|Standing seam||Yes, standing seam metal panels are considered the most compatible option for solar panels. The racking system can be clamped directly to the raised seams without drilling any holes, making the installation much easier.|
|Cedar shingles and shakes||Yes, but keep in mind that cedar shingles/shakes can be vulnerable to fire, especially when the roof is old. If you use solar panels, make sure you get a professional installation to minimize the risk of electrical faults. You should also get a fireproofing treatment.
If you have the budget, a roof replacement is an even better option to reduce fire risks.
|Clay / concrete tiles||Yes, but keep in mind that some tiles may break, even when working with a professional installer.
In this case, some tiles must be removed to make space for the racking system mounts, which attach directly to the roof structure.
|Synthetic tiles||Yes, solar panels can be installed with a standard penetrating mount.|
|Flat roofs (e.g., EPDM rubber, PVC, TPO)||Yes, but solar panels are less productive when they face directly upward, unless the system is close to the equator. You will need tilt-up brackets for your solar panels to reach an optimal angle.
You can use standard penetrating mounts, but ballast systems are also an option, since the roof is flat – the solar racking system is simply held in place with concrete weights.
|Asbestos tiles||Not recommended, due to the health risk involved. The fibers released when drilling asbestos tiles are extremely hazardous. You should upgrade to a safer roof material before installing solar panels.|
Regardless of the roofing material, solar power systems bring several benefits. Since sunlight is being converted into electricity by the panels, it no longer hits the roof directly. This makes your home more comfortable, especially during the summer months, while helping you save on air conditioning.
Installing Solar Panels on Roofs: Frequently Asked Questions
How Do Solar Panels Attach to a Roof?
In most cases, you will use a standard penetrating mount. Holes will be drilled on your roof, to insert the studs that hold the slack racking system in place.
No drilling is necessary if you have a standing seam metal roof, since the racking system can be simply clamped in place.
If you have a flat roof, you also have the option of a ballast system – there is no drilling involved, and solar panels are held in place with weights.
How Do Solar Panels Affect My Roof?
Your roof should suffer no damage during the installation process if you contact a qualified solar provider. However, keep in mind that some roof tiles may break if they’re made of a fragile material like clay or slate.
Does Installing Solar Panels Affect My Roof Warranty?
Generally, your roof warranty is unaffected when a solar installation does not involve drilling. For example, a standing seam metal roof will not lose its warranty if you use clamps to hold the racking system in place.
If the home solar system uses a penetrating mount, you should contact your roofing contractor or manufacturer first. You may be able to keep the roof warranty if solar panels are installed by a qualified provider, and your roofing provider coordinates with them during the process.
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