Can photovoltaic panels be installed at 90 degrees

In general, solar panels should be installed so the sunlight hits them at as close to a perpendicular 90-degree angle for as long as possible during the day. For most of the continental United States, this means angles between 25-45 degrees. The photovoltaic cells absorb the most solar energy available at that instant when the sun's rays strike. . Historically, the advice for finding the best angle for solar panels has been to set your tilt angle equal to your latitude. Using latitude is a good rule of thumb. But we can also get slightly better solar panel angle estimates using free online tools. [pdf]