The SAF units are the new single-block thermo-accumulators for the production of instant domestic hot water, equipped with inverter circulator, electronic adjustment card and stainless steel plate heat exchanger, which ensures maximum hygiene by separating the drinking water circuit from the technical water circuit. The high insulation minimises energy dispersion. These devices have been designed to be combined with heat pumps but also with traditional or biomass boilers, solar thermal systems and other renewable sources. The accumulator can be fitted with an additional coil to integrate an additional heat source, as well as a dedicated circulator and a control software.