Is vertical balcony solar worth it?

Yes in sunny, high-price places. A vertical south-facing panel makes roughly two thirds of what an optimally tilted one would, but costs nothing extra to mount and is often the only allowed option.

Do east or west facing balcony panels work?

They make about half to just over half of a 20° south-facing panel when hung vertically, in our model. They spread production into the morning or evening, which can raise the share you use yourself.

Does a north-facing balcony work?

Hung vertically, a north-facing panel makes about a quarter of a south-facing tilted panel in our model. We would not recommend it.

Balcony solar orientation, tilt and shade: how much each costs you

On a balcony you rarely get to pick the ideal angle. The railing decides. So the useful question is how much each compromise costs. We modeled every common combination of tilt and facing so you can see it at a glance.

Yearly energy at each tilt and facing, relative to a 20° south-facing panel in the same place, at about 39° N (Denver, Washington DC, Kansas City). The outlined row is the typical balcony setup: panels hanging flat on a railing. Modeled by Balcony Solar Atlas with pvlib (Perez sky model) on typical-year weather; see the data and method.

What the numbers say

Vertical on a south railing: about two thirds. Near 39° N, a panel hanging flat makes about 68% of what it would at a 20° tilt facing south.
Southeast or southwest barely matters. Turning 45° from south costs only a few percentage points at any tilt.
East or west vertical: about half. Roughly 53% near 39° N. Production shifts into the morning or late afternoon.
Tilting out helps most. Angling a south-facing panel to 35° on a stand lifts it to about 100% of the reference, half again as much as hanging it flat.
North is a poor bet. A vertical north panel makes about a quarter.

Latitude changes the picture

Vertical panels do relatively better the farther north you are, because the winter sun is lower. In our model, a vertical south panel makes about 57% of the reference in Miami, 65% in North Carolina and 83% in southern Alaska. The calculator interpolates between these by your state’s largest city.

Shade

Shade costs more than its share. A shadow over part of a panel can cut that panel’s output sharply, because the cells are wired in series. Rules of thumb:

A railing post, a neighbor’s balcony slab or a tree that covers the panel for a few hours a day can cut yearly output by a quarter or more.
Panels with more bypass diodes and one microinverter per panel limit the damage to the shaded panel only.
Watch where the shadows fall at 10 a.m., noon and 3 p.m. before choosing where to hang panels. Winter shadows are longer.

Ways to win energy back

Use a tilting bracket if your building rules allow it. Even 60° instead of 90° helps; near 39° N that raises a south panel from about 68% to about 94%.
Mount on the sunniest part of the railing, away from the slab above.
Keep the panels clean. Balcony panels collect dust and pollen.
Split panels across two faces of a corner balcony to catch morning and afternoon sun, if each panel has its own microinverter.

How we modeled it

We used pvlib, an open-source solar modeling library, with the Perez sky model and a ground reflectance of 0.2. Weather came from the typical-meteorological-year files bundled with pvlib for Miami, Greensboro and Sand Point, Alaska. Each value is yearly sunlight on the tilted surface divided by the value for a 20° south-facing surface at the same site. The scripts and results are in our orientation data page.