To reduce the carbon dioxide foot print, it is unescapable to adopt an energy policy that incorporates simultaneously renewable energy systems as well as smart energy strategies such as heat recovery. In the frame of this view, a heat recovery approach is suggested. The heat is recovered from drain water. It is then utilized to enhance the performance of heat pump within two schemes. Directly by replacing the ambient air heating the evaporator and indirectly by preheating the air heated by the condenser. The suggested approach is a numerical and experimental method that, on one hand, relies on experiments to determine the temperature of the drain water and on the other hand, it uses an iterative procedure to solve the energy balance equation and the mass balance equation. To that end an in-house code is developed. It allows to evaluate the heat efficiency of the heat recovery system as well as the performance of the heat pump. It has been shown that using such system may enhance the Coefficient of Performance up to 400%. In addition, economic and environmental studies are performed to assess the economic and environmental impact of the proposed techniques. (C) 2018 Elsevier Ltd. All rights reserved.