The battery-powered applications, such as home thermostats, electronic toys, security systems, in which the battery must last for years together are obvious applications for which power consumption is most important. As these systems become increasingly power-conscious, the need for smart power management becomes equally significant and demand for usage of ultralow power embedded microcontroller unit (MCU) is rising. The choice of MCU is critical. This paper discusses key MCU low power features such as low power capabilities, flexible clocking systems, event-driven resources that affect its performance and provides selection criteria to choose the right one. It also focuses on hardware/software techniques to achieve intelligent power management exploiting the most important feature, any ultra-low power MCU should have—transition and recovery between its low power and active mode.