The basic difference between single and double breast pumps is whether the pump is designed to allow for the expression of milk from one breast at a time or both breasts at the same time. Single breast pumps are better suited for women who want to pump occasionally in addition to traditional breastfeeding. Single pumps can be used at the same time you are feeding your baby, keeping your supply up and preventing your unused breast from becoming engorged. Double breast pumps tend to be a bit more expensive and best suited for women who want or need to pump on a consistent basis. Double pumps can essentially cut your pumping time in half because you are able to express from both sides simultaneously.