"Energy Regulator"?...

...!
In some countries with an unstable/unpredictable Mains Power Supply, you may require the use of an external "Voltage Regulator" to ensure a stable Voltage to your equipment.
The other device which is sometimes used, is a "Surge Protector", mainly to prevent damage from Lightning Strikes to the Power Lines, creating high Voltages in the Power Supply, and damaging your equipment.
In Great Britain, our Mains Supply Voltages and Frequencies are maintained within very strict, closely controlled
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.