In the past it was assumed that a fast wake-up time meant low power. However, in reality it is the activity profile that will govern the overall system power usage. In most low power systems the device needs to perform some operation and go into a sleep mode. It is during this sleep mode that the current consumption is at a minimum. Therefore, it is desirable to remain in the sleep mode for the majority of the time, thus the overall average current consumption will be reduced. There are two ways to achieve the goal of remaining in the low power state most of the time.  Fast wake-up time is one method, fast execution time and autonomous peripherals is another. To minimize the area under the average current curve, decreasing active time is better than decreasing peak current because no matter how much the peak current is decreased, it will not be as efficient as switching to an inactive mode. Some reasons include bias currents, leakage current, etc.