How much do panel orientation, tilt angle and shading matter?

The angle at which your panel faces the sun matters a lot, and so does whether anything shades it. Which way up you hang the panel makes no difference: portrait or landscape, the cells receive the same light, and the choice is usually decided by your space constraints or the length of your mounting brackets rather than by performance.

One thing to watch if you have two panels: they share a single microinverter input in parallel, so mounting them at noticeably different angles means the weaker one can drag down the pair. Match them where you can.

What tilt should I use?

Steeper in winter, shallower in summer, because the sun sits lower in the sky in the colder months. Members adjusting seasonally often move to as flat as 20 degrees for summer and as steep as 70 degrees in winter. If you would rather set it once, pick something in between and accept a small loss at both ends.

Do vertical panels work?

Yes, and they are a normal arrangement on a balcony or deck railing or fence. Vertical mounting does relatively better in winter, when low sun strikes the panel at a favorable angle. In absolute terms winter output is still lower, though, because the days are shorter and cloudier.

Is south-facing the best orientation?

A south-facing mount will generally maximize year-round production. However, if you want to mount your panels vertically or at a very steep angle and have the choice between a roughly south-facing and a more west-facing orientation, choose west-facing. Although you will collect less sun, you will collect it during the later part of the day, when electricity tends to be more expensive and you use more of it, and the sun is lower in the afternoon and early evening hours and hits your vertical panel at a more favorable angle. Just watch out for shading from trees or neighboring homes, especially in winter.

How much does shade cost me?

More than people expect. Partial shade on one panel affects the pair, so a railing that is clear at noon but shaded at three o'clock is worth noticing before you mount anything.

Should I chase the sun through the day?

Not worth it. Pick the orientation that gets the longest clear run of direct sun and leave it alone.

This topic comes up a lot in the Bright Saver Community, where people share photos of their setups and pick each other's mounting apart in the friendliest possible way.