The heat recovery you obtain with this device varies from 30% to 75% depending on the length in size installed (it is possible to use more exchangers in a series or parallel) and water flow. Performance has been measured with the support of the experimental tests done in the University of Padua*.
The cost, of both purchase and installation, allows a quick return on the investment (5 to 10 months for intensive hot water use to a maximum of 2 – 3 years for very low use). With solar panels the same results in terms of savings costs are achieved with greater investment!
(*) test condition: 17° C aqueduct, 40° C sampling point.
This parameter depends greatly on the storage temperature and installation diagram. Without a doubt, Diagram B is the one that allows maximum energy savings. In this case, if the heat exchanger is placed at a distance from the drain point, a certain loss of heat from the pipes during the transitory phase must be taken into account (which only significantly affects cases of very short or discontinuous withdrawals of hot water). As for diagram A, the recovery efficiency mainly depends on the hot storage temperature (boiler).
Localized interventions on single use are the simplest to perform and are usually tied to Diagram A, therefore, they have higher energy efficiency in the case of medium – high storage temperature. Diagram A, if built into the appliance to be used (for example a shower), presents the obvious advantage of a very short connection and therefore minimizes heat losses.