Multi-threshold voltage CMOS (MTCMOS) has emerged as an increasingly popular technique for reducing the leakage energy consumption of idle circuits. The MTCMOS circuits, however, suffer from high energy overhead during the transitions between the active and standby modes. A new circuit technique is proposed in this paper to lower the energy overhead of these mode transitions for effective energy reduction with the MTCMOS circuits. The charge stored at the “virtual power” and “virtual ground” lines are recycled during the active-to-sleep-to-active mode transitions with the proposed technique. Applying the charge recycling MTCMOS circuit technique to a 32-bit Brent-Kung adder reduces the energy overhead due to the mode transitions by up to 36.3% as compared to the conventional MTCMOS circuits. Furthermore, the standby mode power consumption is reduced by up to 91.1% as compared to a standard Brent-Kung adder in a 65nm CMOS technology.