Eggersdorf bei Graz, Austria

Multi family house | 48 sqm installation

Project summary only


Project summary · Technical description · Financing · Development · Downloads

Project Summary

Terraced buildings in Eggersdorf are completely supplied with renewables: backup heating of the solar thermal system is done by a wood chips boiler. The storage tank volume is 6,000 litres.

The heat supply is realised by a 2-pipe plumbing with decentralised heat transfer units in each dwelling.



Type of building

Multi family house

Number of users / dwellings, floors

12 users
2 floors

Year of construction


Total effective area (heated)

approx. 1,500 m2

Hot tap water consumption (measured/estimated)

475 m3/a
(1.3 m3/d)

Whole energy consumption for heating purpose after CSTS implementation

145,800 kWh/a

System engineering

Year of construction of CSTS


Type of collectors

Flat plate collectors

Thermal power

30 kWtherm.

Aperture area of collectors*)

43 m2

Buffer storage

6 m3

Hot tap water storage

2.4 m3

Total capacity of boilers with energy source

110 kW, wooden chips

Type of hot tap water heating


Type of heating system



Total cost solar system

29,300 Euro

Cost of the CSTS / gross area of collectors

610 Euro/m2


not available


Output of solar heat**)

18,960 kWh/a

Reduction of final energy***)

23,700 kWh/a

t CO2-emissions avoided

1 t CO2/a

Solar performance guarantee


*) Aperture area = light transmitting area of the front glass
**) measured, between storage and piping to taps (solar system output)
***) related to the measured output mentioned before




Gemeinnützige Wohn- und Siedlungsgesellschaft Schönere Zukunft Steiermark Ges. m. b. H., Graz


Bäuerliche Heizgenossenschaft


Architekt Fiedler, Graz


Zivilingenieurkanzlei DI Fischer


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Annotation to Good Practice examples from Austria

Concept definition and monitoring as well as system adjustment of the presented project have been done within the framework of "OPTISOL – accompanied monitoring in demonstration projects for optimised and standardised solar systems for residential buildings", financed by the Austrian Federal Ministry of Traffic, Innovation and Technology ("Haus der Zukunft"), by the Austrian Federal Ministry of Economics and Labour and the Federal State Steiermark.