From the Directive 2009/125 / EC (Eco Design) of the European Parliament various Regulations have been derived which have oriented the manufacturers of Products powered by Electricity on the concept of Seasonal Efficiency, i.e. an efficiency not at a fixed, nominal operating condition, but during the entire annual operating period of the Product.

The seasonal indices were therefore created for machines for heating (SCOP = Seasonal Coefficient of Performance) and for cooling (SEER = Seasonal Energy Efficiency Ratio).

The performance of multipurpose machines, i.e. machines that Clivet also offers on the market and that are able to produce cooling and heating simultaneously and independently, are now evaluated on the basis of these two indices, as there is no specific seasonal efficiency index. This situation penalizes them considerably on the market, as the extraordinary efficiency of the simultaneous production of cooling and thermal energy does not emerge.

To fill this gap, the R&D Teams of two competing companies, Clivet and Swegon, cooperated with the aim of developing a possible method for calculating this index and then testing the machines to evaluate their real performance.

The STER (Seasonal Total Efficiency Ratio) was therefore defined as a seasonal energy efficiency index which also takes into account the simultaneity of the heating and cooling requests.

The results were presented both within Assoclima and Eurovent, which decided to create a Task Force to deepen the subject and arrive at a formal proposal to the European Commission to draw up a specific Regulation for Multipurpose machines. After an initial resistance, especially from some historical competitors, other important international companies in the sector have already joined the task force.

The University of Padua also took part in the project with the Master's Degree Thesis of Lorenzo Ottone who, for its realization, carried out an internship in Clivet R&D (Tutor Giovanni Ruggeri) and is now part of the Clivet family.