Sliedrecht, Netherlands

Multi-family house | 180 sqm installation

Project summary only


Project summary Technical description Financing Development Downloads

Project Summary


Social housing association Tablis Wonen realised a 180 m2 collective solar thermal system on the roof of one of their apartment complexes with 160 apartments in two blocks. Due to a switch from individual kitchen tap water heaters to a collective solar hot water system, the comfort and indoor climate of the apartments has been improved significantly. The increase in warm water comfort does not lead to higher energy costs for tenants as this is compensated by the solar hot water system. Installing solar thermal systems fits in the sustainability policies of Tablis Wonen.




Type of building

Multi-family house

Number of users / dwellings, floors

160 dwellings
10 floors

Year of construction


Total effective area (heated)

17,490 m2

Hot tap water consumption (measured/estimated)

4,140 m3/a (calculated)

Whole energy consumption for heating purpose after CSTS implementation

356,700 kWh/a

System engineering

Year of construction of CSTS


Type of collectors

Flat plate collectors

Thermal power

125 kWtherm.

Aperture area of collectors*)

179 m2

Buffer storage

6 m3

Hot tap water storage

2 m3

Total capacity of boilers with energy source

690 kW (natural gas)

Type of hot tap water heating


Type of heating system



Total cost solar system

102,860 Euro

Cost of the CSTS / gross area of collectors

575 Euro/m2


58 %


Output of solar heat**)

82,040 kWh/a

Reduction of final energy***)

117,200 kWh/a

CO2-emissions avoided

22 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



Andy Nijkerk, head real estate:

"The net costs for our tenants did not increase, while the comfort and living conditions have improved significantly. The tenants are very happy with the new hot water supply. We only received positive responses. Many housing associations are looking for good solutions for hot water heating. This collective solar hot water system is a solution that will get follow-up."






Housing association Tablis Wonen
P.O. Box 145
3360 AC Sliedrecht, Netherlands

System manufacturer 

Itho BV
P.O. Box 21
3100 AA Schiedam, Netherlands


GTI Utiliteit
P.O. Box 2064
2990 DB Barendrecht, Netherlands

Top of page Project summary Technical description Financing Development Downloads



this datasheet in printable PDF-format

270 K