Due to dramatically increasing energy need traditional grid becomes inadequate to manage the energy generation and distribution system. Smart Grid is an efficient, user-friendly solution to today's energy management and generation problem. However, Smart Grid introduces many privacy issues that do not exist in traditional grids. For example, with Smart Grid it is possible to obtain consumers' daily life patterns from their energy usage data. In this paper, we tackle with this problem and propose a novel privacy-preserving communication protocol. The proposed protocol is based on time perturbation and Shamir's Secret Sharing (SSS) scheme. In the proposed protocol, consumption reports are generated by smart meters and sent to a data collection center using Laplace Distribution based time perturbation. In addition, SSS is employed to prevent attacks during multi-hop data transmission. The time perturbation prevents malicious users to see the actual data while it is stored in the data center. Security analysis shows that the proposed protocol preserves privacy of consumer data during both data transmission and data storage.