You might notice that some solar panels are mounted in landscape (horizontal) and some are mounted in portrait (vertical). Why is that, and how should you mount yours? The answer might surprise you, and it’s actually quite important.
We see a lot of contractors mounting solar panels in landscape orientation because rectangular panels just fit better on a triangular or trapezoidal roof. You can often squeeze another panel or two (or more) when placing them in landscape orientation. Some also consider this to be a more aesthetically pleasing way to mount solar panels, although I disagree and prefer portrait installations. But which one is better?
First and foremost, it is important to realize that the aluminum rails that solar panels are mounted on should be placed perpendicular to the roof trusses. It is more common to have vertical roof trusses, although not always. Because trusses are predominantly vertical, rails are predominantly horizontal. It is possible to mount rails horizontally where trusses are also horizontal, and there are various ways to accomplish that.
If the rails are horizontal, you may still be able to mount solar panels horizontally if the engineering says it is okay. However, that is often not the case. Some installers ignore that fact. If you think about it, the panels are connected to the rails at only 4 places. If you connect the panels on the short ends, there is a very long span between the ends of the panel. That increases the flex of the panel in high winds. Most module manufacturers test their solar panels for wind load and there is a “sweet spot” along the long side of the panel where it can handle the greatest loads.
That is why, in most cases, it is highly preferable to mount solar panels in portrait orientation with horizontal rails. This is especially important in Southwest Florida where design wind speeds are very high. What you get is a lot of out-of-town, or even out-of-state solar companies selling and designing systems in Florida without this expertise. It’s another reason you really need to hire a local expert. Aside from theory, there is anecdotal evidence from Hurricanes Irma and Ian that landscape panels had more issues than portrait panels.