How this is calculated
Each city carries twelve monthly figures for the sunlight landing on a flat surface and twelve for how much of it is diffuse, from the European Commission’s PVGIS 5.3 database. The Hay and Davies sky model turns those into the sunlight striking your panels at their real tilt and direction.
That is multiplied by the module rating and a performance ratio of 0.81 for heat, wiring, dust and inverter efficiency, then held to 800 W at every moment of the day.
Kilowatt-hours used at home are the annual total times your self-consumption share, the saving is those times your price, and the payback is what you paid divided by the saving. The twenty-year line charges 0.5% degradation a year.
Worked example. Munich, two 430 Wp panels on a 30° bracket facing due south, unshaded: 968 kWh a year. At a 60% self-consumption share, 581 kWh lands on the household’s own load, worth €168 at €0.29. A €450 kit is repaid in 2.7 years and clears about €2,760 over twenty.
Use your own price. The European medium-household average including all taxes was €0.2896 in the second half of 2025 (Eurostat half-yearly series), Ireland dearest at €0.4042, Hungary cheapest at €0.1082 — full table in the price of a kilowatt-hour everywhere.
Quick answers
How long does a balcony kit take to pay for itself?
Two 430 Wp panels facing south in Munich clear a €450 kit in under three years at a 60% self-consumption share and €0.29 a kilowatt-hour. Halve the share, double the payback.
How much does a balcony kit generate in a year?
For 860 Wp due south: 453 kWh in Reykjavik, 684 in Munich, 928 in Madrid on a vertical railing; 581, 968 and 1,420 on a 30° bracket.
Does the self-consumption share beat the panel rating?
Against a steady 150 W draw in Munich, the bracket generates 42% more than the vertical mount and puts 9% more on the bill.
How much does a vertical railing mount lose?
Between 19% and 41% of the year across the 31 cities here, averaging 30%. From December to February it wins almost everywhere north of the Alps.
Can a balcony kit power anything in a blackout?
No. The inverter must disconnect within a fraction of a second when the mains goes away, and nothing then reaches the socket.
Why is the limit 800 W?
Commission Regulation (EU) 2016/631 starts its smallest generator class at 0.8 kW, below which a generator is too small to matter to the network.
Where the 800 W ceiling comes from
Germany’s rule, as the consumer advice centres state it, caps the inverter at 800 W of AC output and allows up to 2,000 Wp of module behind it. Great Britain took the same figure in its announcement of 24 March 2026, citing 426,269 German balcony registrations in 2025 — Bundesverband Steckersolar’s reading of the Bundesnetzagentur register. The cap sits on the inverter alone, so a kit may carry more glass than the inverter can ever pass.
What over-paneling costs, modelled here. With 1,720 Wp behind an 800 W inverter, the ceiling throws away 3% of the year in Munich and 16% in Madrid on a 30° bracket — but nothing in Munich and 2% in Madrid on a vertical railing, which never reaches it.
The 2,000 Wp allowance is a gift to a vertical mount and a trap on an angled one in the south. The panel datasheet guide covers which rating on the box you are buying.
Why the share used at home outranks the panel rating
A balcony kit has no meter of its own. Its power joins the flat’s wiring and is subtracted from whatever the house is drawing at that instant. The rest leaves through the meter, and in most of Europe a plug-in device is paid nothing for it.
| Steady household draw | Vertical railing, 684 kWh made | Angled 30°, 968 kWh made |
|---|---|---|
| 100 W | 350 kWh used · 51% | 373 kWh used · 38% |
| 150 W | 477 kWh used · 70% | 522 kWh used · 54% |
| 200 W | 578 kWh used · 85% | 650 kWh used · 67% |
| 300 W | 680 kWh used · 99% | 832 kWh used · 86% |
| 400 W | 684 kWh used · 100% | 936 kWh used · 97% |
Munich, 860 Wp due south, modelled hour by hour at a constant draw. A real household is lumpier, which pushes every share down a little.
At a 150 W draw the bracket makes 284 kWh more than the vertical mount and delivers 45 kWh more to the bill. Forty-two percent more energy buys nine percent more money.
Germany’s consumer advice centres put it in round numbers: one unshaded 400 W module on a vertical south balcony makes about 280 kWh a year and takes about 200 kWh off the bill.
What a vertical railing mount really costs
Across the 31 cities here, standing the panels upright gives up 30% of the year against tipping them out to 30°. The loss runs from 19% in Trondheim to 41% in Nicosia and Valletta, growing southward because a steep panel is a poor match for a high sun.
The flat line is the point. A vertical panel loses the summer, when the flat is least likely to want the power, and holds up in the dark months, when every kilowatt-hour lands on a load that is running.
From December to February it beats the bracket by 11% in Munich, 14% in Groningen and Manchester, 20% in Aarhus and Riga, about 37% in Ostersund and Trondheim. Only around the Mediterranean does the bracket still win those months. The tilt angle calculator runs the same trade-off for a full-size array.
The kit goes dark when the grid does
A plug-in inverter is grid-following. It takes its voltage and frequency reference from the mains, and when that reference disappears it stops within a fraction of a second. The reason is a lineworker on the pole: a generator feeding a dead circuit would energize the section being repaired.
That protection lives in the connection code, which is why Great Britain’s route to legal plug-in kits runs through an update to G98 and to the BS 7671 wiring regulations, announced 24 March 2026.
That makes a balcony kit a bill machine and nothing else. Light and a fridge through an outage need hardware built to run islanded — size that with the power station calculator, and read power station against generator.
Moving a kilowatt-hour to when it is wanted
Every kilowatt-hour moved into the sunlit hours is worth the full retail price. The smart plug is the cheap version: run the dishwasher or the water heater at midday. Two or three loads a week moved that way beat a third panel.
A battery has to earn its price. Divide its cost by the kilowatt-hours it will shift over its life: a €600 unit moving 300 kWh a year for fifteen years costs €0.13 a kilowatt-hour moved, which beats a €0.29 tariff and loses against a €0.11 one. The true cost of a stored kilowatt-hour runs that properly.
A battery does not turn the kit into backup power. Most charge and discharge through the same grid-following inverter and shut down with it.
Shade from the balcony above
The slab over your head blocks sun above a certain elevation, and the geometry is a paper job. Measure how far the slab edge sticks out in front of the top of your panel and how far it sits above that point: sun steeper than the angle whose tangent is height over projection is blocked.
Hang the panel outside the railing and the slab edge is almost directly above it: 1.1 m up, 0.2 m out, a cut-off near 80°. The sun never gets that high in Europe.
Lean the same panel against the back wall and the numbers invert: 1.4 m up, 1.5 m out, a cut-off near 43°. The Munich noon sun clears 43° from late March to the third week of September, so that panel loses the middle of every good day for half the year.
Yield by city and mounting
Every figure is for 860 Wp facing due south, held to 800 W of inverter output, performance ratio 0.81. Click a heading to sort.
| City | Lat °N | Vertical 90° kWh/yr | Angled 30° kWh/yr | Free-standing kWh/yr | Vertical penalty | Dec–Feb, vertical vs angled |
|---|---|---|---|---|---|---|
| Nicosia, Cyprus | 35.2 | 874 | 1478 | 1478 at 31° | −41% | -5% |
| Madrid, Spain | 40.4 | 928 | 1420 | 1427 at 36° | −35% | +7% |
| Valletta, Malta | 35.9 | 825 | 1408 | 1408 at 30° | −41% | -4% |
| Athens, Greece | 38.0 | 852 | 1392 | 1393 at 32° | −39% | -1% |
| Lisbon, Portugal | 38.7 | 845 | 1362 | 1363 at 33° | −38% | +1% |
| Rome, Italy | 41.9 | 862 | 1307 | 1313 at 36° | −34% | +7% |
| Sofia, Bulgaria | 42.7 | 745 | 1133 | 1136 at 34° | −34% | +1% |
| Lyon, France | 45.8 | 751 | 1112 | 1117 at 36° | −32% | +7% |
| Zagreb, Croatia | 45.8 | 712 | 1066 | 1070 at 35° | −33% | +6% |
| Budapest, Hungary | 47.5 | 715 | 1043 | 1048 at 37° | −31% | +7% |
| Cluj-Napoca, Romania | 46.8 | 711 | 1041 | 1046 at 36° | −32% | +3% |
| Bratislava, Slovakia | 48.1 | 694 | 1023 | 1027 at 36° | −32% | +6% |
| Ljubljana, Slovenia | 46.1 | 665 | 1001 | 1003 at 34° | −34% | +6% |
| Vienna, Austria | 48.2 | 683 | 994 | 999 at 36° | −31% | +8% |
| Zurich, Switzerland | 47.4 | 682 | 994 | 999 at 36° | −31% | +7% |
| Munich, Germany | 48.1 | 684 | 968 | 975 at 38° | −29% | +11% |
| Prague, Czechia | 50.1 | 658 | 936 | 942 at 37° | −30% | +10% |
| Brussels, Belgium | 50.9 | 643 | 898 | 905 at 38° | −28% | +11% |
| Warsaw, Poland | 52.2 | 628 | 891 | 897 at 37° | −30% | +10% |
| Groningen, Netherlands | 53.2 | 617 | 847 | 855 at 39° | −27% | +14% |
| Aarhus, Denmark | 56.2 | 611 | 832 | 841 at 40° | −27% | +20% |
| Vilnius, Lithuania | 54.7 | 591 | 829 | 834 at 38° | −29% | +12% |
| Riga, Latvia | 57.0 | 612 | 828 | 839 at 41° | −26% | +20% |
| Tartu, Estonia | 58.4 | 608 | 811 | 823 at 41° | −25% | +24% |
| Galway, Ireland | 53.3 | 570 | 778 | 784 at 38° | −27% | +14% |
| Manchester, England | 53.5 | 550 | 754 | 759 at 38° | −27% | +14% |
| Ostersund, Sweden | 63.2 | 570 | 719 | 737 at 45° | −21% | +37% |
| Jyvaskyla, Finland | 62.2 | 553 | 715 | 730 at 43° | −23% | +34% |
| Inverness, Scotland | 57.5 | 524 | 690 | 698 at 40° | −24% | +21% |
| Trondheim, Norway | 63.4 | 533 | 659 | 678 at 46° | −19% | +39% |
| Reykjavik, Iceland | 64.2 | 453 | 581 | 591 at 42° | −22% | +34% |
Computed from PVGIS 5.3 monthly irradiation with a Hay and Davies sky model. Free-standing uses each city’s annual-optimum tilt, shown beside the figure. Spot-checked against the PVGIS 5.3 PVcalc service on 3 September 2026 at 14% system loss: Munich 30° returns 972 kWh against 968 here, Munich vertical 699 against 684, Madrid 30° 1,385 against 1,420, Reykjavik vertical 456 against 453 — every check inside 3%. Compare the raw sunlight in the peak sun hours atlas.
Sources
PVGIS 5.3 monthly irradiation and the PVcalc service, European Commission Joint Research Centre; Eurostat household electricity prices, second half of 2025 (medium consumption band, all taxes included); Verbraucherzentrale guidance on Steckersolar devices; Commission Regulation (EU) 2016/631 article 5(2)(a); the British government’s plug-in solar announcement of 24 March 2026. All re-checked 3 September 2026.
Go deeper
Plug-in balcony solar explained covers the rules country by country. For what the same money buys in hardware that works when the grid stops, use the power station calculator. The off-grid solar payback period shows how storage changes the arithmetic, and what panels lose in 25 years explains the 0.5% charged above.