How do I know if my balcony gets enough sun for solar?
Watch the spot across one clear day and count the hours it sits in direct sun with nothing in the way. That count decides what a kit will make, more than your zip code. Plug-in solar is a panel you hang on a balcony railing, a wall or a fence and plug into an ordinary household outlet, so nobody surveys the site for you.
Our savings calculator gives you a figure from your zip code, but it assumes direct sunlight all day, no shading, and ideal orientation and tilt, so treat that as the ceiling.
PVWatts, the free calculator from the National Renewable Energy Laboratory, gets you closer. Enter your address, set the system size to 0.18 kW for one 180 W panel or 0.36 kW for the two-panel 360 W kit, set the tilt and the direction the panel faces, and it returns estimated output month by month.
Then apply your own discount. PVWatts does not model the tree in front of your building or the roof next door, and NREL says its estimates do not reflect site-specific characteristics. Say it gives you 430 kWh a year for your address and tilt, and your railing loses about a third of its direct-sun hours to a neighboring roof. A third off 430 is roughly 287, so plan on something near 290. Weight the discount toward the middle of the day, because an hour lost at noon costs you more than an hour lost at eight in the morning, when the sun is low and its light travels through more atmosphere.
How many hours of direct sun do I need?
There is no single threshold. A panel produces whenever light reaches it, so the useful question is how much, not whether. Run the arithmetic above for your own spot, then compare the annual kilowatt-hours against the per-kilowatt-hour rate on your electricity bill.
Does the savings calculator account for my shade?
No. It works from your zip code, and it says on the page that the estimates assume direct sunlight all day, no shading, and ideal orientation and tilt. It gives you the rate side of the calculation. Your own count of sunny hours supplies the other side.
Does the panel produce anything on a cloudy day?
Yes, less. Panels respond to diffuse light as well as to direct light, so output falls on an overcast day without stopping. Note the weather on the days you count, because one grey week will make a good spot look poor.
Will winter look different?
Yes. The sun sits lower, shadows run longer, and a railing that is clear in July can be in shade for most of a January afternoon. If you can, check the spot again closer to the winter solstice before you decide where to mount.
What if my only spot does not face south?
Direction matters less than an unbroken run of sun. We go through orientation, tilt and shading in a separate answer.
Can I skip all this and just install it?
You can, and the first week will tell you a lot. The inverter app reports what the inverter is putting out, hour by hour. It reports inverter output only, so it cannot show what your household is using and it cannot show what goes to the grid.
Members post photos of shaded railings and first-week output in the Bright Saver Community, which is the quickest way to see what a spot like yours actually produces.