Security in wireless sensor network (WSN) has become an increasing necessity due to the diverse application areas being implemented. Application areas such as military surveillance and environmental monitoring need to be guided against node tampering and node subversion. Works carried out by wireless sensor network researchers pertaining to increasing the security of the network is significant. Node authentication is a suitable technique against node tampering and the introduction of false nodes. A way of authenticating nodes is by using Message Authentication Code (MAC); this is implemented using hash functions. The limited energy available to sensor nodes, have to be considered when selecting a hash function for implementation. In this paper, comparative analysis of some hash functions (MD-5, SHA-1, SHA-224, SHA-256, SHA-384 and SHA-512) were carried out. The functions were selected based on their popularity. The analysis was done to identify a short-list of hash functions that can be used when WSN hash related security techniques are being designed. The short-listed functions so identified were further analyzed in terms of their complexities. This was carried out by executing compiled codes and averaging the CPU time spent in executing a common scenario. The result of the analyses showed SHA-224 as the best hash function to be used when designing energy-conscious secured WSNs.