If your roof is completely flat, it is strongly recommended to install the panels at an angle of at least 10 °. This is very important as it allows rainwater to flow down from the module. If rainwater accumulates on the surface of the solar panel, it is more likely to eventually pass through the panel's seal and enter the solar cell itself. If this happens, the panel will malfunction and you will need to replace the module. The warranty condition for many panels is that they must be installed at least 10 ° from the horizontal, otherwise it may result in warranty failure.
Don't listen to anyone saying that solar panels can be placed horizontally, just add one or two panels to compensate for the efficiency loss. Horizontal panels have almost no self-cleaning ability in the rain, so you need to manually clean them more frequently.
Tilting the frame on a flat roof is a good approach. But sometimes installers will propose inclined frames for roofs with already small gaps to increase the angle of the panels and gain more energy. If you really want to lay these panels flat, then there is one option: frameless panels. These are panels without aluminum frames. This means that there are no ridges around the panel to collect dirt and water. However, frameless panels are more expensive.
For these reasons, if you have a flat roof, most excellent installers will add the option of a sloping frame in their quotation.
Is the tilt angle really important? Answer: Yes.
The tilt of solar panels will affect the power they generate, as the tilt will affect the sunlight you capture. Consider a flat solar panel on the ground with a width of 1 meter. When the sun is in the middle of the sky (such as at noon in summer), that solar panel will fully capture a 1-meter wide solar axis: now, if the sun is at a 30 ° angle to the horizontal, the same 1-meter wide axis will actually unfold more than 2 meters when it hits the ground: in this example, a flat solar panel will only receive half of the sunlight, thus generating half of the energy compared to the sun directly overhead. Of course, the solution in this example is to tilt the panel 60 ° to capture all sunlight
