The quality of service (QoS) in Smart Grid (SG) communications has a significant importance on emerging SG applications. Wireless sensor networks (WSNs) were considered as a compatible choice to fulfill this issue. In fact, WSNs could be widely used in a wide range of smart grid applications because they have been successfully adopted in several critical areas. Unlike other WSN applications, SG requires precise estimation of specific topologies and performance parameters such as the end to end (E2E) delay. In this paper, we perform a complete analysis of the E2E source-sink delay considering a cluster-tree topology. For this analysis, an autoregressive filter is used to estimate the average values of delay. The main contribution of this work is to perform a better interaction between physical, MAC, network and application layers for SG E2E communications. Our method is based on the assumption that the E2E delay is calculated after sending a beacon using the Markov model and considering Rayleigh fading channels.