The solar compact installation enables the heat transfer medium to be circulated in the solar circuit between the collector and the cylinder heat exchanger. It comprises all essential components for the hydraulic circuit. In connection with the SOKI SAS cylinder connection set, it can be fitted directly to the SBB .. plus/basic cylinder. It is provided with thermal insulation to minimise heat losses. An integral non-return valve prevents the undesirable thermo-siphon effect, i.e. the solar cylinder does not lose its heat when the circulation pump is idle. At any time, an optical flow meter enables the checking of the flow rate that can be regulated via the different pump stages. A safety valve (6 bar), indicator thermometer for flow and return, shut-off valves for flushing, filling and draining the system, connection for an expansion vessel and a wall retainer are included.