Balcony solar: calculating the yield and orienting it correctly

1What is allowed in 2026: 800 watts, 2,000 watt peak, plug

In Germany, balcony solar kits – called “Steckersolargeräte” (plug-in solar devices) in the law – are subject to two limits. Section 8 (5a) of the Renewable Energy Sources Act (EEG) names an installed capacity of up to 2 kilowatts in total and an inverter power of up to 800 volt-amperes in total. In practice: modules with up to 2,000 watt peak combined, and at most 800 watts go into the home circuit. Both values apply per connection point; several devices count together.

Electricity you do not use yourself flows into the grid free of charge. There is no feed-in tariff for it; in return, the grid operator may not demand any additional registration. The device is only entered in the Federal Network Agency's market master data register (Marktstammdatenregister) – within one month of commissioning, with just a few details. The grid operator learns about it from there.

The plug question was clarified by the product standard DIN VDE V 0126-95, in force since 1 December 2025: a household plug (“Schuko”) is permitted if the device has the protective measures provided for it. With a household plug, however, the standard limits module power to 960 watt peak. To use the full 2,000 watt peak you need a special energy plug connector. Devices already in operation are not affected by the standard.

Finally, the old meter: a Ferraris meter without a backstop may keep running temporarily until the metering operator replaces it. You do not have to wait with your balcony kit.

2How much a vertical module delivers per kilowatt peak

The key figure in any yield calculation is the specific annual yield: kilowatt hours per kilowatt peak of module power. For a south-facing roof tilted at 35 degrees it is around 1,000 in Germany. For a vertical module on a railing it is considerably lower, because in summer the sun comes steeply from above and strikes the vertical surface at a shallow angle.

The table shows the values for vertical modules, calculated with the PVGIS hourly data that the SolarFinder calculator also loads. Facing south, vertical modules in Germany reach around 670 to 790 kilowatt hours per kilowatt peak – about 70 percent of what the same surface would produce at a 35 degree tilt. Facing east or west it is around 470 to 550, roughly half.

For an 800 watt balcony kit with two modules totalling 800 watt peak, multiply by 0.8: facing south in Frankfurt, 732 times 0.8, so around 590 kilowatt hours a year; facing west, 501 times 0.8, around 400.

3Vertical on the railing: less in summer, more in winter

That a vertical module produces less is only half the story. It also produces differently. In winter the sun is low and hits a vertical south-facing surface almost head-on. In the weather year 2019, a vertical south-facing module in Frankfurt produced 41 kilowatt hours per kilowatt peak in December, one tilted at 35 degrees only 36. In June it was the other way round: 68 against 141.

Over the year, a quarter of the vertical south module's yield falls in November to February, compared with only a sixth for the tilted module. Between February and September the vertical surface delivers almost the same amount month after month. For a balcony kit without storage that is an advantage: the power arrives more evenly, and less of it goes unused into the grid at midday in summer.

If you are allowed to tilt the modules, you still gain a lot. At 35 degrees facing south, the same 800 watt kit in Frankfurt delivers around 840 instead of 590 kilowatt hours. Brackets on the railing must be securely fixed, though – a module weighs 20 to 25 kilograms and offers the wind a large surface. Whether the landlord or the owners' association allows tilting is the second question.

For east and west balconies winter is no consolation: the low sun then stands in the south-east and south-west and strikes the surface at an angle. There, November to February accounts for only around 13 percent.

4The direction of the balcony: what each orientation brings

You cannot change the direction, but you should know it before buying modules. The table shows an 800 watt balcony kit in Frankfurt, vertical on the railing, for a household consuming 2,000 kilowatt hours a year without storage – exactly as the calculator computes it with the starting values below.

South is best, as expected; south-east and south-west lose only four to nine percent. East and west deliver a quarter to a third less than south. The right-hand column is striking: a larger share of an east balcony's yield is used directly, because the power arrives in the morning when the coffee machine and kettle are running. The gap in electricity actually used is therefore smaller than the gap in yield.

A north-facing balcony is unsuitable for a balcony kit. Vertical modules facing north receive almost only diffuse light; the investment hardly pays back over the lifetime.

Open in the calculator: 800 W, vertical, facing south

5More modules than 800 watts: what 2,000 watt peak brings

Since the module limit rose to 2,000 watt peak, many retailers offer kits with four modules on one 800 watt inverter. That sounds wasteful, because the inverter clips in full sun. But vertically on a balcony, full power is rare – the modules almost never reach their rated output.

The calculator shows this as inverter clipping. In Frankfurt, vertical and facing south, 2.0 kilowatt peak on 800 watts delivers around 1,310 kilowatt hours a year, more than twice the 586 of 0.8 kilowatt peak. Only around 150 kilowatt hours are clipped. Facing east it is 971 instead of 432, facing west 923 instead of 401.

Less of it is used directly than the figures suggest, however: in the example household with 2,000 kilowatt hours, self-consumption facing south rises only from 415 to 576 kilowatt hours; the rest goes into the grid unpaid. More modules pay off mainly if someone is at home during the day or a battery shifts the surplus into the evening.

And the standard sets a limit: with a household plug, new devices may only have 960 watt peak. For four modules you need the special energy plug connector.

Open in the calculator: 2.0 kWp on 800 W, vertical

6Shading: the factor no calculator knows

On a balcony, shading is the rule, not the exception. In summer the balcony above casts a shadow on the upper part of the modules, your own parapet on the lower part, and in winter the house opposite on everything. Trees that are in leaf in summer are often bare in winter.

PVGIS takes the horizon from terrain data into account – mountains and hills, but no houses, no trees, no balcony above. The SolarFinder calculator does not know your balcony either. You have to estimate shading yourself and deduct it from the yield.

A simple method: on a sunny day, watch from when to when the sun falls on the spot where the modules are to hang. If it is only free from 1 pm, a vertical south balcony loses around 40 percent of its yield – that is how much it produces in Frankfurt before 1 pm summer time. Winter matters most: if the sun stays behind the neighbouring house in December, the advantage of vertical mounting is gone.

Technically, an inverter with two separate inputs, one per module, helps. Then a shaded module does not drag the other one down. For modules hanging one above the other and partly shaded, it is also worth checking the bypass diodes on the data sheet.

7How much you use yourself – and what it saves

For a balcony kit, only the electricity you consume yourself counts. What goes into the grid earns nothing, because there is no tariff for it. The saving is therefore the electricity used directly times your electricity price – not the annual yield times the price.

In the example above, a household with 2,000 kilowatt hours uses around 70 percent of a vertical south balcony's yield itself, and almost 80 percent on an east balcony. The base load from fridge, router and standby devices absorbs a large part. At 35 cents per kilowatt hour, that is €116 to €145 a year.

How quickly the device pays for itself depends on the price: divide the purchase price by the annual saving. The calculator does this under “Total cost”: the preset is the shop price of a kit matching the system and battery size you set, or an estimate if there is no matching price. Enter the price of your offer there and it calculates with that.

8Registration, landlord, owners' association

After plugging in, you have one month to register in the Marktstammdatenregister. It is done online in a few minutes; the Federal Network Agency has reduced the details for plug-in solar devices to a few fields. Registration with the grid operator is not required in addition.

Under Section 554 of the German Civil Code (BGB), tenants can demand that the landlord permits structural changes for a plug-in solar device – unless this is unreasonable for the landlord. The landlord may have a say in the how, such as the fixing or the look of the facade. Under Section 20 of the Condominium Act (WEG), flat owners have a corresponding claim against the owners' association, which decides on the implementation.

So ask beforehand, but do not expect a fundamental no. And agree on the fixing in writing: a falling module is a liability case.

9Calculating your balcony in the calculator

The links in this guide open the SolarFinder calculator with starting values for a balcony kit: 0.8 kilowatt peak, an 800 watt inverter, 90 degree tilt, no storage, 2,000 kilowatt hours consumption, no feed-in tariff. The location is yours; set the direction on the slider or measure it with your phone.

The calculator immediately shows an estimate from a simple model that derives irradiation from latitude. After one or two seconds it loads the PVGIS hourly values for exactly your location and orientation and simulates the whole year hour by hour, including inverter clipping. The figures in this guide are such PVGIS values.

For vertical east and west balconies, the first estimate is ten to 25 percent above the PVGIS value. What counts is the value that remains after loading. Without a connection to PVGIS the estimate stays; the printout states which data basis was used.

Note: the PVGIS data describe a single year, 2019. It was sunnier than average; averaged over 2005 to 2020, yields are up to five percent lower depending on location.

Open in the calculator: 800 W, vertical, facing east