Heating without gas in Vienna: what does the ground say at your address?

In short: The City’s geothermal map is green on 54 % of Vienna’s area and yellow on 46 %; a geothermal borehole needs a water-law permit on 77 % of the area, a groundwater heat pump everywhere. A groundwater body suitable for thermal use lies beneath 62 % of the city. Of the 1,108 funded heat pumps in the City’s register, 754 take their heat from the air — none of these maps applies to them.

What the City’s energy maps show

The City of Vienna publishes its energy maps as open data. Four of them matter for a heat pump: the map for geothermal boreholes with the water-law permit zone and the thermal conductivity of the ground, the map for groundwater heat pumps with the output class per pair of wells and the groundwater bodies suitable for thermal use, the sewers for waste-water heat and the climate protection areas of the energy spatial plans.

Green, according to the City, means use generally possible. Yellow: further information needed. Magenta: use generally not possible. Where several restrictions overlap, the map shows the strictest. How much heat can actually be gained is not part of the map, above all for groundwater; underground car parks and other underground structures are not fully known to it. City of Vienna, geothermal cadastre

Shares of the area each map covers; own calculation from the City’s maps, retrieved 13 October 2026.

Three points, three answers

Azima shows the same short form at every address under “Heating without gas” — here at three points:

In Grinzing the groundwater map is green, yet no groundwater body suitable for thermal use lies there. That is why Azima always reads the map, the output class and the groundwater body together — the map colour alone does not say so.

What applies — and what does not

• New buildings have not been allowed fossil heating since 29 February 2024 (federal Renewable Heat Act). City of Vienna, energy spatial plans
• In the climate protection areas of the energy spatial plans, heating and hot water in new buildings may only use energy from renewable sources, efficient district heating or carbon-free sources; existing buildings are not affected. According to the City, a climate protection area is still a sign that district heating is well available. City of Vienna
• Whoever converts a building, carries out a major renovation or changes the heating system has to cover the energy demand from renewable sources, efficient district heating or carbon-free sources, as far as that is technically, functionally and economically feasible; a qualified person checks this (§ 118c of the building code, in this version since 15 July 2026, in substance since 2023). RIS
• Merely replacing the gas boiler in a flat with a newer appliance does not change the heating system, according to the explanatory notes to the building code. Vienna Parliament, 26 June 2026
• New oil or coal heating is not permitted in a renovation or a change of the heating system (§ 118c (6)).
• An official date on which gas ends in an area or at an address could not be found as of 13 October 2026. The Vienna Heat Plan 2040 shows which heat supply is best suited in which area; according to the City it is non-binding. City of Vienna
• A groundwater heat pump always needs a water-law permit in Vienna; a geothermal borehole needs none in the west of the city and one everywhere else — it has to be reported everywhere. City of Vienna, water-law permit
• Whether a district heating connection is possible is checked case by case by Wien Energie. City of Vienna

What the City pays for the switch

The City (MA 50) funds the switch to a high-efficiency alternative heating system in your main residence with 35 % of the recognised cost, at most 5,250 euros in a flat and at most 8,000 euros in a single-family house, where geothermal, groundwater or waste heat adds 4,000 euros and income limits apply; the old system has to be removed and the new one has to be the only heating. Whoever frees the flat from gas entirely and cancels the gas connection can also get a decarbonisation bonus of usually 1,000 euros, 1,500 euros if the whole building switches. In apartment buildings, wohnfonds_wien funds at most 50 euros per m² of floor area, at most 80 euros with geothermal, groundwater or waste heat, plus 4,000 euros per connected flat, capped at 35 % of the cost, applied for before construction starts. Payment depends on the available budget and there is no legal entitlement; the federal boiler-replacement scheme takes no more applications for 2026, the environment ministry has announced 179 million euros for 2027, and the conditions had not been published as of 13 October 2026 (as of October 2026).

Sources, retrieved 13 October 2026: MA 50, heating systems, decarbonisation bonus, wohnfonds_wien, federal renovation scheme, environment ministry, 13 July 2026. The same line, with its date, is in Azima under “Heating without gas”.

Funded installations by district

The City keeps registers of funded installations: 1,108 heat pumps (built 2016 to 2023), 6,088 solar power and 2,844 solar thermal systems. Of the heat pumps, 754 work with the outside air (air-to-water), 278 with ground heat via brine (brine-to-water) and 76 with water as the heat source (water-to-water). Funded heat pumps per 1,000 buildings are most common in Margareten (14.4), Donaustadt (8.5) and Penzing (8.2), least common in Mariahilf (0.0).

Counted per district, never a single house. Installations without funding are missing from the registers; the heat-pump register runs to 2023, the solar thermal one to 2021. Buildings: City of Vienna roof model (LOD2.1).

Frequently asked

Solar potential per roof · Green roof potential · What the house still allows · EV charging

Sources: City of Vienna energy maps — geothermal borehole and thermal groundwater use maps, geothermal potential, thermal groundwater potential map, suitable groundwater bodies, waste-water heat potential, funded heat pumps, solar power and solar thermal systems (data.gv.at, CC BY 4.0, retrieved 13 October 2026; data source: Stadt Wien – data.wien.gv.at); District boundaries and roof model: City of Vienna (CC BY 4.0); law: RIS and wien.gv.at; funding: wien.gv.at, wohnfonds_wien, sanierungsoffensive.gv.at. No legal advice and no planning — the maps replace neither a specialist nor a permit.