An energy saving alternating current series voltage regulator for regulating an AC output voltage from an AC output power source, characterized in comprising: an AC high frequency series voltage buck power regulator topology for bucking an AC input voltage of an AC input power source; a bypass contactor system; a bidirectional AC semiconductor device connected in parallel with the bypass contactor system, wherein the switching response time of the bidirectional AC semiconductor device is faster than that of the bypass contactor system; a control circuitry for receiving the AC input voltage, the AC output voltage, and generating driving signals for the bypass contactor system and the bidirectional AC semiconductor device; wherein the control circuitry is configured to continuously monitor the AC input voltage level against a selectable energy saving level corresponding to an optimum energy saving setting; wherein under a condition of the AC input voltage falling below a selected optimum energy savings set level, the control circuitry sensing the condition, generating driving signals to activate the bidirectional AC semiconductor device and to transition the bypass contactor system such that the bidirectional AC semiconductor device initially bypasses the AC HF series voltage buck power regulator topology, then the bypass contactor system contacts close and fully bypass the AC HF series voltage buck power regulator topology and the bidirectional AC semiconductor device; and wherein under a condition of high load surge or fault currents, the control circuitry sensing the condition, generating driving signals to activate the bidirectional AC semiconductor device and to transition the bypass contactor system such that the bidirectional AC semiconductor device initially bypasses the high load surge or fault currents away from electronics of the energy saving AC series voltage regulator, then the bypass contactor system contacts close and fully bypass the high load surge or fault currents away from electronics of the energy saving AC series voltage regulator and the bidirectional AC semiconductor device to an external breaker. an AC high frequency series voltage buck power regulator topology for bucking an AC input voltage of an AC input power source; a bypass contactor system; a bidirectional AC semiconductor device connected in parallel with the bypass contactor system, wherein the switching response time of the bidirectional AC semiconductor device is faster than that of the bypass contactor system; a control circuitry for receiving the AC input voltage, the AC output voltage, and generating driving signals for the bypass contactor system and the bidirectional AC semiconductor device; wherein the control circuitry is configured to continuously monitor the AC input voltage level against a selectable energy saving level corresponding to an optimum energy saving setting; wherein under a condition of the AC input voltage falling below a selected optimum energy savings set level, the control circuitry sensing the condition, generating driving signals to activate the bidirectional AC semiconductor device and to transition the bypass contactor system such that the bidirectional AC semiconductor device initially bypasses the AC HF series voltage buck power regulator topology, then the bypass contactor system contacts close and fully bypass the AC HF series voltage buck power regulator topology and the bidirectional AC semiconductor device; and wherein under a condition of high load surge or fault currents, the control circuitry sensing the condition, generating driving signals to activate the bidirectional AC semiconductor device and to transition the bypass contactor system such that the bidirectional AC semiconductor device initially bypasses the high load surge or fault currents away from electronics of the energy saving AC series voltage regulator, then the bypass contactor system contacts close and fully bypass the high load surge or fault currents away from electronics of the energy saving AC series voltage regulator and the bidirectional AC semiconductor device to an external breaker.