Modern smart grid implementations bring several advantages in terms of operational controls. Distributed generation and storage facilities near the load centers are probably the most important concepts that are used to improve the quality and the reliability of the consumed energy. Siting and sizing of DG generations in distribution systems may create several problems in traditional radial power systems, which were originally designed for unidirectional power flows. This paper presents an optimal DG allocation and sizing approach in a traditional distribution network where the whole year load variation is taken into account. Optimization aims to minimize both the total voltage variation, TVV, in a day and daily percentage energy losses along the feeder branches. The two objectives are first formulated as singular optimization problems and then combined in a multi-optimization problem. Meta-heuristic Cuckoo search algorithm is used to solve the resulting constrained optimization problem. The proposed formulation is applied to a 12-bus radial distribution system and the MATLAB simulations are performed to validate the performance of the approach.