Refrigeration is an essential sector in our daily lives, accounting for 15-20% of global energy consumption, according to data presented by the European Cool-Save project. It therefore accounts for a significant fraction of the CO2 emissions emitted worldwide and, at the same time, plays an essential role in the progress of society.

As in other sectors, we are increasingly looking for greater energy efficiency in our refrigeration systems, with the aim of reducing our costs while reducing our energy demand and greenhouse gas emissions. To know the efficiency of our installation, the most representative indicator is the instantaneous efficiency of a refrigeration machine or heat pump (η), defined as the quotient between the cooling capacity, or heating capacity in the case of a heat pump (Q), and the electrical power of the compressor (Wcomp):

In the case of the efficiency of a refrigeration machine, it is usually called EER (Energy Efficiency Ratio); and in the case of a heat pump, it is called COP (Coefficient of Performance).

When it comes to calculating this instantaneous efficiency in practical terms, two methods can be distinguished: the direct method and the indirect method.