The Diario dei consumi (Consumption Diary) is the tool introduced in 2019 to support the reduction of domestic consumption, similar to what has already been experimented in the energy field on the basis of Thaler's behavioural theories. It is an experimental project, developed together with the �Department of Management, Economics and Industrial Organization� of the Politecnico di Milano, which analyses the behavioural interactions of individuals, trying to enhance positive and virtuous behavior. In 2020, the service was extended to about 65,000 additional customers and now involves 145,427 residential customers (about 20% of all residential customers).There are synergies among different resources that make the consumption of one resource dependent on that of the others. Some of these synergies are technological, e.g. in the case of household appliances that consume both water and electricity (positive synergies); other interactions, on the other hand, have behavioural roots, such as for example the desire of individuals to behave consistently in different contexts (positive synergies) or in the presence of cognitive limitations that prevent individuals from paying attention to all the resources consumed at the same time (negative synergies). If positive synergies prevail, a decrease in the consumption of one resource causes a decrease in the consumption of other resources, while the opposite occurs if negative synergies dominate.A report is sent to them, via email, which analyses their consumption patterns in detail, comparing the volumes of water used by the individual customer with that of similar customers and the change in the customer's consumption over time. The report is also complete with tips to help customers choose some good functional water-saving household practices. Activation of the Diario dei consumi (Consumption Diary) will be gradual and over the next four years will involve all users who have provided their e-mail address to Hera Group.