Energy saving of small cells is an important issue for a mobile network deployed with a large number of small cells. These small cells are typically overlapped with macro cells. When the call traffic is light, a small cell enters the dormant mode to save energy. Therefore, its call traffic is directed to the overlapped macro cell. When the traffic load of the macro cell becomes heavy, the macro cell wakes up the dormant small cells to share the traffic load. It is a nontrivial task to wake up the 'right' dormant cells. This paper proposes simple energy saving (SES), which is a simple yet novel scheme, to accurately wake up the dormant small cells. In a low-traffic environment, our scheme enables the small cells to quickly enter the dormant mode. When the macro cell is heavily loaded, it wakes up the dormant small cells to share its traffic load. Specifically, with 90% of energy saving in our scheme, a dormant small cell can be detected and reported to the macro cell in 1.3716 s. When the macro cell conducts the wakeup mechanism, with a probability of 0.9, more than 75% of the dormant small cells are not affected and can stay in the dormant mode. We also show that energy saving of the SES scheme is more effective when the macro cell covers a larger number of small cells.