Solar potential in Vienna: does a panel make sense on this roof?
The City of Vienna has calculated every roof in the city from a 25 cm surface model — including the shade cast by neighbours, trees and terrain. This page explains what the figures mean; the address check reads them for one roof.
Most solar calculators start with the roof’s orientation and its tilt. In a city that is the smaller half of the answer: what decides a Viennese roof is what stands next to it. A south-facing roof with a five-storey neighbour eight metres away can be worse than a flat roof three streets on. Vienna measured exactly that — the whole city, from the air, once — and published the result.
What can your roof do? Solar power in euros, worked out for your address — free, no account:
The address goes to the City of Vienna address service for the search, never to Vienna Living Map. The result stays on this device. No account.
Four classes, and what they mean
A roof is rarely one class. It usually carries several: a very good south pitch, a good east pitch, a shaded strip behind the stairwell. That is why the useful figure is not the average — it is how many square metres lie above the good threshold. A large roof with one perfect surface beats a small evenly mediocre one, and the average hides exactly that.
For the example house on Schrankgasse in the 7th district the cadastre gives 1,138 kWh/m²·a as the roof average, 99 m² in the good and very good classes together, and up to 6 kWp — around 5,700 kWh a year by the rule of thumb. Two houses further on the figures are different, and that difference is the whole point of a cadastre.
The solar cadastre calculates the roof; for a flat below it, what counts is the sun at the window — check the hours of sun per room before you buy a flat.
Frequently asked
How does the City of Vienna calculate this?
From a digital surface model at 25 cm resolution — a laser-scanned image of the city including roofs, trees and terrain. For every square metre the model works out how much solar energy arrives over a year, with everything that stands in the way already subtracted. That is why the figure differs from a simple orientation rule: the neighbouring building is in it.
What does kWp mean, and what comes out of it?
kWp is the rated output of the array, not its yield. In Vienna an array delivers about 1,000 kWh per kWp per year (about 970 facing east or west, up to 1,175 tilted south, according to the EU tool PVGIS) — so a 6 kWp roof produces around 6,000 kWh. That figure is a rule of thumb: tilt, orientation, module quality and shading move it, and only a planner’s calculation replaces it.
Does this work for a single flat?
Not on your own. The roof belongs to the building, so an array needs the owners’ association — which is exactly why the figure is more interesting before a purchase than after. For a whole house, a Zinshaus or a new development it is a number with money attached.
What does the cadastre not know?
Statics, the state of the roof covering, monument protection, the grid connection and who owns what. It answers one question — how much sun arrives up there — and that question is the precondition for all the others, not a substitute for them.
Where do I see the figure for my address?
In the light check: enter the address, and the roof of that building is looked up in the cadastre — square metres per suitability class, mean irradiation and the possible output. It also lands in the PDF report.
The same roof, greened · Heating without gas · Cool living · The light check · All districts
Source: solar potential cadastre of the City of Vienna (2022), calculated from the 25 cm surface model — data.wien.gv.at, CC BY 4.0. Suitability classes as published by the City. The yield rule of thumb (1,000 kWh per kWp per year) is an estimate, not a measurement. No planning and no offer: statics, monument protection, the owners’ association and the grid connection all have a say.