In this paper, we present a detailed analytical study of previously proposed variable preamble length-based broadcasting scheme for wireless sensor networks (WSNs). Analytical results show that in dense wireless sensor networks, broadcasting a packet with a small size preamble can significantly improve the energy conservation on already limited battery powered sensor nodes. For fairer comparison with variable preamble length-based broadcasting scheme, a comprehensive analytical study for an existing probability-based broadcasting scheme is also presented. Analytically calculated results show that variable preamble length-based broadcasting scheme is more energy-efficient than the probability-based broadcasting scheme.