Can Solar Panels Be Laid Flat?

Yes, solar panels can be installed successfully on a flat roof of a home or company. Solar PV panel systems can be installed on flat roofs with a small slope allowance. A 1/4:12 pitch roof is defined as a roof with a rise of 0.25 inch over a 12-inch run. Flat roofs are also known by the following terms:

When designing and installing flat roof solar panels, solar panel installers face a variety of obstacles.

Here’s a quick rundown of the five things you should know before installing solar panels on your flat roof.

Is it possible for me to lay my solar panels flat?

Solar panels can, in fact, be mounted flat. Certain inverters can employ flat-mounted panels instead of traditional mounting techniques, which are normally positioned at an inclination on the roof.

Is it better to have flat or angled solar panels?

The vertical tilt of your solar system is referred to as solar panel angle. Your solar panels, for example, would have a 90-degree angle tilt if they were perpendicular to the ground. Solar panels should be positioned to face as close to the sun as possible in order to capture solar energy more efficiently. When the angle at which the sun’s rays contact the panel surface (the “angle of incidence”) is modest, or when light strikes the panel as close to perpendicular as feasible, photovoltaics generate electricity. As a result, the optimal solar panel angle is one that permits the panels to receive the most direct, perpendicular light.

What factors affect your optimal solar panel angle?

The optimal angle of your solar panels is affected by a variety of factors. When deciding on the appropriate tilt for your solar array, keep the following factors in mind:

Latitude

The majority of solar panels are positioned at an angle that maximizes sunlight exposure for that particular area. For the vast majority of property owners in the United States, the best angle for a solar panel installation is between 30 and 45 degrees, which is close to or equal to your home’s latitude (on a south-facing roof). You may ensure that you get the maximum average output from your solar power system throughout the year by tilting your solar panels at the same angle as your home’s latitude (which means aiming your panels at that average location).

New York versus D.C.

For instance, we analyzed data from two locations (New York and Washington, D.C.) and calculated the production levels of solar panels slanted at various degrees. What we discovered was in line with our previous research on the effects of other variables:

  • Solar power offers huge savings regardless of where you reside or the angle of your roof.
  • The direction your solar energy system faces has a greater impact on solar panel performance than the pitch of your roof.
  • Solar panels facing south at a slant of 30 degrees provide the most electricity. Even if you tilt your roof all the way down to 5 degrees, though, production only drops by around 10%.

** Assumes a derate factor of 80%, a 180-degree azimuth, and an array tilt equal to the latitude of the location.

Existing roof design

It would be ideal if everyone’s roof was inclined at the same angle as their latitude, however each home is different, and there is no common solar panel placement map. Many roofs will have a slope of 30 to 40 degrees, allowing solar panels to be installed flush against the roof and produce enough electricity to generate attractive returns.

If you’re trying to install solar panels on a steep roof, typical racking solutions may not be able to arrange panels at the appropriate inclination. The best you can do is lay your panels flat against the roof because the steep angle of your roof may already be greater than the optimal angle for production. Low-angle roofs will also face challenges when it comes to solar panel installation, and if you want to tilt them at the best angle, you’ll need specialist racking. When panels are installed flush against these sorts of roofs, less electricity is produced, resulting in lower solar savings over time.

When installing solar panels on a flat roof, solar installers will typically utilize racking equipment to position your panels at an appropriate angle. While this permits your panels to face the sun more directly, the size of your system may be limited as a result. If you tilt panels up on a flat roof, they will shade each other until the rows of panels are spaced and staggered out on the roof. As a result, you won’t be able to install as many panels as you would if the solar panels were flush with the surface.

It’s usually ideal to have a professional solar installer install the panels on your roof, regardless of whether your roof is steep or flat, to ensure optimal production and safety. Also, if you’re not sure how solar panels might work for your home and roof type, read this article to see if you’re a suitable candidate for solar.

Is it necessary for solar panels to be angled?

Because your panels create the most energy when the sun is directly perpendicular to them, the tilt of the panels is crucial. The sun is low in relation to the horizon in the northern hemisphere during the winter, for example. In this scenario, a sharp angle of 60 is ideal for the solar panels to work at their finest. The optimal angle in the spring is 45 degrees, and in the summer, when the sun is high in the sky, it’s better to have a low tilt of 20 degrees!

What is the efficiency of flat solar panels?

Previously, panel manufacturers would not provide warranties for panels put at angles less than 2 degrees, but today, the majority of the top manufacturers will provide warranties even if their panels are positioned at 0 degrees (completely flat).

In Australia, however, industry standard practice is to slant the panels at least somewhat so that they can better’self-clean’ when it rains. It’s also worth remembering that many roofs are naturally slanted aluminum roofs, for example, typically have a 3-4 degree slope. The most common roofs that are genuinely horizontal are concrete or membrane roofs, in which case a tilt or ballast mechanism is typically utilized to give the panels at least a 10-degree pitch.

If your roof is truly flat, there are a few instances where putting your panels horizontally (or almost horizontally) can be worthwhile. These are the following:

  • If the structure on which the panels will be installed is in the tropics beneath 23 degrees latitude. This is because the sun’s motions through the tropical sky mean that during the summer months (late December to late March in the southern hemisphere), the sun may be to the south of your roof. The midday sun, on the other hand, never moves south of a system over 23 degrees latitude. If you live in the tropics, the closer your system is to the equator, the more time the sun is ‘behind’ your roof. The more of this winter sun you can catch if your panels are arranged horizontally (or close to it). (However, to reduce dust gathering, a small pitch is still ideal.)
  • If your roof space is restricted. Even if you don’t live in the tropics, if your roof is flat, it may make sense to install your panels horizontally rather than paying more for tilt frames. Surprisingly, setting your panels level in Sydney (rather than north-facing at a 33-degree inclination, which is optimum) reduces efficiency by roughly 10%-12%, while tilt frames can increase the cost of your system by about the same percentage. Before you make a decision, make sure you do the math – the higher your latitude (for example, if you reside in Tasmania), the more tilt frames are likely to be worthwhile.

A note about dust accumulation on flat solar panel arrays

Another issue to keep in mind if your panels are horizontal is that they will not self-clean as well as panels that are tilted dust will have a larger possibility of gathering and interfering with power production. The reduction in performance caused by dust deposition on panels is estimated to be between 5% and 10%. When it rains, though, solar panel arrays inclined at an inclination even if it’s only a modest angle are more likely to be washed clean.

How can solar panels get installed on a flat roof?

As seen in the table, mounting panels at a 10 degree angle produces between 52 and 72 percent more power per unit amount of roof space (once the spacing required between rows is taken into account).

Optimal panel orientation for flat roof solar

Solar panels installed in the UK will produce the most power when oriented between 30 and 40 degrees and facing straight south, as previously stated. But what if your house doesn’t have a south-facing roof? Shouldn’t the panels be facing south anyway? What about an east/west arrangement?

South-facing systems

Solar panels on a flat roof can be oriented as much as 90 degrees off south, facing directly east or west, and still be worth considering in terms of output performance, just as they can be on a pitched roof.

In order to attain the maximum number of panels within the roof space, it is normally advisable to align the panels with the footprint of the building. Rotating the array to face due south has little value because it wastes space that could be utilized to put more panels. Please see the images below.

We can get 30% additional panels in the previous scenario by installing in line with the roof footprint (allowing for suitable edge distances). In comparison, the less favorable orientation resulted in only a 0.5 percent loss in output (20 degrees off south).

It’s worth noting that the output differential between panels installed directly south and panels mounted east or west is substantially lower at a 10 degree pitch than it is at a 30 degree pitch – see table above.

East/west systems

An east/west structured system is another mounting option to consider for buildings with footprints aligned roughly south. These systems employ the identical A-frames as the south-facing systems, tilted at 10 degrees, but put back to back such that the panels are oriented at 180 degrees from each other (due east and west ideally).

Because no intervals are required between rows, east/west systems maximize the power output (number of panels) per square metre of roof. The greater capacity compensates for the poorer performance of the individual panels due to the less favorable orientation. A 10 degree east/west system outperforms a 10 degree south-facing system by up to 25% in terms of per unit area.

In addition to the performance advantages, east/west systems require less ballast. East/west systems, on the other hand, are more expensive per kWh than south-facing systems due to the lower performance of individual panels. Despite this, an east/west mounting method is normally preferred for the other reasons described above, provided the building footprint can handle an orientation as close to east-west as possible.

Ballasting

A free-standing ballasted flat roof solar mounting structure is preferable in most cases. The use of a free-standing mounting mechanism held down with ballast eliminates the requirement for roof penetration. This reduces the possibility of roof leakage and guarantees that any warranties on the roof’s watertightness aren’t jeopardized – which is especially crucial if your roof is fresh new.

The solar mounting frames in ballasted systems are supported by specific rubber footings that help distribute the load. Ballast comes in a variety of shapes and sizes, and installation choice may vary. We use precast concrete ballast at Spirit because it is neat and tidy and will endure a long time.

Ballasting, on the other hand, isn’t always a possibility; for example, if the roof can’t support the weight of the ballast, or if the ballast need is so large (e.g., tall structures) that there isn’t enough space under the panels to accommodate it all! There may be no choice but to attach directly to the roof structure. This is more difficult than using ballast since the roofing manufacturer’s input is sometimes necessary to guarantee that the fixings are properly sealed against water penetration. There are devices available, but they normally necessitate the installation of a new roof covering and can be fairly costly.

The roof system manufacturer’s choice of fixing will be determined by their own specialized fixing. Other universal fittings are available; please contact us for more details.

Other considerations for flat roof solar installations

  • Because spacing between rows of panels is required to prevent one row of panels from shadowing another, flat roof systems take up more area per kW than sloping roof systems.
  • The fact that there normally needs to be a 0.5-1m border between the system and the edge of the roof makes space even more limited.
  • Solar panels on flat roofs are commonly ‘free-standing’ on the roof. Because the mounting frames are not attached to the roof, the system must be weighted down with ballast. The ceiling structure must be capable of supporting the ballast.
  • Flat roofs are often used as a storage area for air conditioning systems and lift motor housing on commercial facilities. To reduce shade, they should be avoided. Furthermore, health and safety are always a priority, both during the initial installation and continuing maintenance.
  • Roof warranties are available. It’s critical that the system doesn’t jeopardize the warranty on the roof. A free-standing, ballasted solar system is compliant with the majority of roof warranties. However, some roof types and membranes, such as Bauder roofs, may necessitate the installation of a specialized anchoring mechanism. If the system is fixed to the roof, make sure to evaluate the impact on the roof warranty and maintain water tightness.
  • The state of the roof. It is critical to ensure that the roof is in good working order before adding solar. It’s obviously easier to remove ‘free-standing’ panels from a flat roof than it is to remove bolted panels from a sloping roof; on a flat roof, an upgrade a few years after installation won’t be too disruptive. However, if your flat roof uses ordinary roof felt, it’s worth checking to see whether it’s in good shape before installing solar.
  • Some felt roofs can melt in the heat of summer and then become brittle in the cold of winter. UV radiation can also have an effect on it. As a result, it is prone to leaks and must be replaced every 10 years or so. It may be worthwhile to upgrade the roof membrane prior to installation; there are now maintenance-free membranes available that are guaranteed for 15-20 years and should last 30.
  • Structure of the roof. To comply with Part L of the Building Regulations, all new-build flat roofs must have a warm roof construction. Again, it’s critical that the solar system doesn’t interfere with the warm roof’s operation, and that this is taken into account while building the system.

None of these factors indicate that a flat roof system isn’t worth considering; they merely indicate that the procedure is more difficult, and it’s more crucial than ever that the system is designed and installed by qualified professionals.

We have submitted planning applications for and built a significant number of flat roof systems on a range of properties utilizing various mounting techniques at Spirit, and as a result, we are able to recommend the optimum option for every individual site.

On a flat roof, how is solar installed?

To avoid leaking due to water pooling, there are three ways for placing solar panels on a flat roof.

In the United States, any of the three flat roof solar panel solutions can provide best energy output for solar panels on a flat roof. Flat roof solar panels are possible regardless of the kind of installation because:

A solar panel array can be leveled (leveled panels are visually appealing)

A solution attached to the roof penetrates the surface and connects to the framing. An professional engineering evaluation is always used to establish the best method of solar panel installation on a flat roof.

Is it possible to lay solar panels horizontally?

PV solar generators are installed in more than 2.5 million Australian houses, accounting for roughly 20% of the country’s households. Surprisingly, nearly all home solar panels are installed on rooftops horizontally. Ground-mounted arrays are the obvious alternative, but they require huge open regions that aren’t usually available. However, solar panels can also be mounted vertically on walls or on steeply pitched roofs.

Although uncommon, properly fitted vertically mounted solar panels can generate power and operate just as well as horizontally mounted solar panels. So, when should you use vertical installations instead of flat ones, and what are the drawbacks?

On a flat roof, what angle should solar panels be installed?

Solar panels on flat rooftops must be positioned at a slant that gathers as much sunlight as possible while also keeping the panels clean. Self-cleaning is feasible by placing the panels at an angle of at least 10 degrees.

Why is it necessary to tilt solar panels?

PV panels gather solar energy from the sun, the sky, and sunlight reflected off the ground or the region surrounding the PV panel. The collection efficiency of a PV panel can be increased by tilting it in a direction that maximizes direct sunlight exposure. When the sun’s rays are perpendicular to the panel’s surface, the panel will capture solar radiation most efficiently. The sun’s angle changes throughout the year, as seen in Figure 9. As a result, the best tilt angle for a PV panel in the winter will be different than the best tilt angle in the summer. The angle will change depending on the latitude.

PV panels are built directly into the luminaire housing in some PV lighting systems, such as solar garden lights or small post-top luminaires, and cannot be relocated or orientated in a specific direction. PV panels are normally positioned horizontally, towards the sky, in these types of installations. Many bigger PV lighting systems, on the other hand, are built to allow a system installer to tilt the PV panel at an angle from horizontal and orient it in a specific direction. A system specifier or installer should first identify the ideal tilt angle and orientation of the PV panel for the system’s placement in these types of systems.

Reviewing the location where the PV lighting system will be built is the first step in establishing the best PV panel orientation and tilt angle. At different times of the day or during the winter months when the sun is at a low angle in the sky, trees, huge buildings, or other objects or impediments surrounding the site may cast shadows onto a tilted PV panel. As a result, it’s possible that orienting the PV panels horizontally to face the sky directly is the best option. This may allow the panels to absorb as much solar energy as possible with the least amount of hindrance. A horizontal panel, on the other hand, will become soiled more quickly.

If the area around the PV lighting system is largely clear of barriers, however, a lighting specifier can point the PV panel in a specific direction and at a specific angle. The PV panel should always face the equator in this instance. The panel should face south in the Northern Hemisphere and tilt from horizontal at an angle about proportional to the site’s latitude (NREL 2005). For example, if the system is in San Diego, California, the PV panel should be facing south and tilted up at a 33-degree inclination.

These tilt angle suggestions are an average, taking into consideration the sun’s angle throughout the year. If a PV lighting system is planned to be utilized in all four seasons at a northern latitude, however, it may be beneficial to tilt the PV panel at an angle that optimizes its performance in the winter, when solar radiation is likely to be at its lowest. PV panels should be angled up from horizontal at an angle 15 degrees greater than the latitude to enhance their performance in the winter. For example, a panel tilted to 48 in San Diego (latitude 33) will allow a 43 percent reduction in panel size compared to a horizontal panel (see “What is the method to determine the suitable size of PV panels for a given application?”).

In contrast, if a PV lighting system will only be utilized during the summer (for example, at a seasonal campsite or state park), it may be more cost-effective to maximize the PV panel’s performance for the summer. The panel should be inclined 15 degrees less than the latitude for best summer performance (NREL 2005).

Unfortunately, there is no clear historical data on the real improvement in system performance that may be achieved by optimum PV panel orientation and tilt. The majority of panel orientation suggestions are based on computer simulations and mathematical models. Performance gains based on improving PV panel orientation and tilt angle are estimated to be between 10% and 40%. (Landau 2002).