As part of a series of studies of aminonitroalkanes, here we present density functional theoretical calculations on the properties of three symmetrically substituted aminonitroethane molecules: aminonitroethane, diaminodinitroethane and triaminotrinitroethane. Key data includes the energy content for combustion and decomposition reactions. Surprisingly, the greater the amount of substitution, the lesser the specific enthalpies of combustion but the greater the specific enthalpies of decomposition.