Energy saving is an important issue in Mobile Ad hoc NETworks (MANETs). Recent studies show that network coding can help reduce the energy consumption in MANETs by using less transmission. However, apart from transmission cost, there are other sources of energy consumption, e.g., data encryption/decryption. In this paper, the network coding is done to reduce the energy consumed by data encryption in MANETs. It is interesting that network coding has a nice property of intrinsic security, based on which encryption can be done quite efficiently.