How Much Power Does a Balcony Solar Panel Produce? US Data

How much power does a balcony solar panel produce? An 800 W balcony kit tilted 35 degrees to the south makes about 931 to 1,446 kWh a year in six US cities, or roughly 2.5 to 4 kWh a day. Hang the same kit flat against a south-facing railing and it drops to about 638 to 887 kWh a year, and an east or west railing makes less again.

Those figures come from the European Commission’s PVGIS calculator, run on US weather data for this post.

Watts vs kWh: what “800 W” on the box means

The watt rating on a balcony solar kit is its power at a given moment, while kilowatt-hours measure the energy it makes over time. The U.S. Energy Information Administration defines one kilowatt as 1,000 watts and one kWh as “one kilowatt generated for one hour.”

So an 800 W kit running at full output for one hour would make 0.8 kWh, by my math. Your bill counts kWh, which is why the yearly kWh figure matters more than the label.

A panel rarely hits that rating, which assumes strong, direct sun. Mornings, evenings, clouds, a steep angle and heat all pull it down, so you can’t multiply watts by daylight hours.

How much power does a balcony solar panel produce per day, month and year?

A typical balcony solar kit of 800 W produces about 2.5 to 4 kWh a day when tilted toward the south in most US cities, and about 1.75 to 2.43 kWh a day on a vertical south railing. EnergySage says most plug-in systems are between 400 and 800 watts.

Kit and mounting	Per day	Per month	Per year
800 W, tilted 35° south	2.55–3.96 kWh	78–120 kWh	931–1,446 kWh
800 W, vertical south railing	1.75–2.43 kWh	53–74 kWh	638–887 kWh
1,200 W, tilted 35° south	3.8–5.9 kWh	116–181 kWh	1,397–2,168 kWh
1,200 W, vertical south railing	n/a	n/a	957–1,331 kWh

The 800 W rows are PVGIS results for Seattle at the low end and Phoenix or Denver at the high end. By my math, the 1,200 W rows are the 800 W results multiplied by 1.5, since output scales with panel size before any inverter limit kicks in.

The tilted range lines up with EnergySage’s estimate that an 800 W system “might produce somewhere between 70—110 kilowatt-hours” a month. Virginia Tech’s Saifur Rahman puts two south-facing 540-watt panels at about 125 kWh in “a clear, sunny month,” Virginia Tech News reports.

Balcony solar output by US city and mounting

Balcony solar output in the US depends as much on how you mount the panel as on where you live. The table shows yearly kWh for an 800 W kit in six cities and four real balcony setups.

City	Tilted 35° south	Vertical, south	Vertical, east	Vertical, west
Phoenix, AZ	1,446	877	692	657
Los Angeles, CA	1,364	820	582	675
Denver, CO	1,308	887	635	585
Miami, FL	1,235	669	622	575
New York City, NY	1,074	725	523	465
Seattle, WA	931	638	423	472

How this was made: I ran PVGIS 5.2 on October 28, 2026, with its PVGIS-NSRDB database, 800 W of crystalline panels and the 14% system loss PVGIS recommends. The PVGIS methods page says this database comes from NREL’s NSRDB, and the weather years are 2005 to 2015. I rounded the results to whole kWh.

Three patterns stand out:

A vertical railing costs a lot. A vertical south panel made 54% to 68% of the tilted result, by my math. That’s a loss of 32% to 46%.
East and west railings make about half. Vertical east or west panels made 43% to 51% of the tilted south result.
Sunny doesn’t always win on a railing. Denver’s vertical south panel beat Phoenix’s, and Miami’s came in below New York City’s.

Why a vertical railing panel makes less

A vertical balcony panel makes less because the sun is high in the sky for much of the year, so its light strikes a vertical surface at a steep, glancing angle. PVGIS also models extra reflection at sharp angles, which its methods page puts at “a loss of 2-4% of sunlight” in general.

The effect is strongest in summer and in the South. In Phoenix, a vertical south panel averaged about 110 kWh in January but only about 27 kWh in June. The tilted panel made 112.85 kWh in January and 122.87 kWh in June.

Germany’s Environment Agency (UBA) reports the same pattern: railing panels give lower yields in summer and slightly better ones in winter. It puts the yearly loss at about 30 percent, or 665 full-load hours instead of 950. That gives an 800 W vertical kit 532 kWh a year.

The US loss is bigger in places like Miami and Los Angeles because they sit much farther south than Germany. German guidance doesn’t carry over to them one for one.

Peak sun hours: the number that drives output

Peak sun hours are the daily solar energy hitting your panel, expressed as hours of full sun. They are the single biggest input to any balcony solar output estimate. PVGIS reports them for the panel’s own angle, which is the figure you want, not the flat-ground number many maps show.

For a 35-degree south panel, PVGIS gives about 6.7 peak sun hours a day in Phoenix, 5.72 in Denver, 4.64 in New York City and 4.06 in Seattle. On a vertical south railing, those fall to 4.11, 3.9, 3.16 and 2.81.

Our balcony solar calculator uses watts ÷ 1,000 × peak sun hours × 365 × 0.86, where 0.86 is the 14% PVWatts default loss. Fed the New York City tilted figure, it gives 1,165 kWh by my math, against PVGIS’s 1,074.

Across the six cities, the formula comes out 9% to 16% higher than PVGIS. The reason: PVGIS also models heat and reflection losses, which the simple formula leaves out. Treat the calculator’s result as an upper estimate.

Shade, heat and other losses

A balcony solar panel loses output to dirt, wiring, heat and shade before its power reaches your outlet. The PVWatts Version 5 Manual from NREL bundles the routine losses into a 14% default.

That 14% is built from these defaults:

soiling 2%, shading 3%, mismatch 2% and wiring 2%
connections 0.5% and light-induced degradation 1.5%
nameplate rating 1% and availability 3%

Shade is the one to watch on a balcony. The 3% shading default reflects distant objects on systems described as “unshaded.” NREL says the value should be raised for shade from nearby trees or buildings, and a balcony above or a privacy wall counts. The UBA warns that even partial shade can cut yield significantly.

Heat trims output on hot days. PVWatts assumes a standard module loses 0.47% of its power for each extra degree Celsius. A panel pressed against a sun-baked wall runs hotter than one with air behind it.

Inverter limits and state wattage caps

The inverter and your state’s wattage cap set a ceiling on what a balcony kit can feed into your home at any moment. Panel watts above that ceiling only help in weak light.

Most US states with a plug-in solar law cap these devices at 1,200 W. That includes Utah’s HB 340 and New Jersey’s S2368. Colorado’s HB26-1007 allows “a maximum power output of not more than” 1,920 watts to the grid. Maine’s LD 1730 lets you install up to 420 W yourself and requires an electrician above that. Germany’s economy ministry sets an 800-watt inverter limit.

When panels can make more than the inverter allows, the inverter clips the peak. NREL’s manual says that “the output is clipped to the nameplate value.” Its default sizes panels 1.1 times the inverter rating, because the extra panel watts catch more energy in the morning and evening. The tables above don’t model clipping, so a kit with more panel watts than inverter watts will lose some midday output.

How to estimate your own balcony’s output

You can estimate your own balcony solar output in a few minutes with PVGIS and a compass.

Find your panel’s direction. A phone compass held against the railing works.
Note the angle. A flat railing mount is 90 degrees; a tilting bracket is usually 30 to 35.
Run PVGIS. Pick your address and the PVGIS-NSRDB database. Enter your panel watts, 14% loss, your angle and your azimuth.
Subtract for shade. If a balcony above or a wall blocks the sun for part of the day, lower the estimate.
Check the inverter. If panel watts exceed the inverter rating, expect some midday clipping.

To turn kWh into dollars, see our balcony solar cost guide and its payback table by state. For how the power flows from panel to outlet, read how balcony solar works.

My take, and the limits of these numbers

My take: if your railing faces south or close to it, spend the extra on a bracket that tilts the panels outward. In this data, tilting raised output by roughly half or more in every city, and in Miami it nearly doubled it. If you’re stuck with an east or west railing, plan on about half the tilted south number and pick a smaller kit.

PVGIS models open sky, so it can’t see the balcony above you, the building next door or a wall that heats up. The PVWatts manual also warns that any single year can differ from the long-term average by up to 20 % for annual totals. Use the table to compare setups, then check it against your own monitoring app. Whether the output is worth buying for is covered in are balcony solar panels worth it.

FAQ

How much energy does an 800 W balcony solar kit produce per day?

In the PVGIS runs for six US cities, an 800 W kit tilted 35 degrees to the south averages 2.55 kWh a day in Seattle and 3.96 kWh in Phoenix. Hung vertically on a south-facing railing, it makes 1.75 to 2.43 kWh a day.

How many kWh does an 800 W balcony solar kit make per month?

About 78 to 120 kWh a month when tilted toward the south in the six cities modeled, close to EnergySage’s 70–110 kWh estimate. A vertical railing mount makes roughly 53 to 74 kWh a month on a south-facing balcony.

Does a vertical balcony solar panel still work?

Yes, but it makes less. Germany’s Environment Agency puts the loss at about 30 percent there. In the US cities modeled here, a vertical south panel made 54% to 68% of what a 35-degree panel made, with the biggest drop in sunny southern cities.

How much energy can a 1,200 W balcony solar kit produce?

By my math, about 1.5 times an 800 W kit: roughly 1,397 to 2,168 kWh a year tilted south in the six cities, or 957 to 1,331 kWh hung vertically, before any inverter clipping.