The aim of this research is to study the behaviorof heat pump installations in order to get relationsbetween operating conditions and the factors that affectthe Performance of these equipments. By operating condi-tions is meant the outside air temperature. This researchfirst reviews the available literature on air-to-air heatpumps and to point out the need for correlations of theperformance of these units under different outside airtemperature’A theoretical analysis was carried out, and anexperimental work was conducted to obtain the soughtcorrelations. These results indicated the sensitivevariation of the performance of the air-to-air heat pumpwith the outside air temperature.We notice, for example that a change of SOC inoutside air temperature decreases, the coefficient ofperformance of heat pump by 29~ , while a change ofS·C in outside air temperature increases, the coeffic-ient of performance of ~efrigeFatiw.rr with 51% •