Light dimming regulator circuit
It is a very standard dimmer circuit.



When used properly (with the right kind of load) it is very efficient as it quickly switches on and off. It is mainly usable for resistive loads which means oldfashioned lighbulbs. It is less suitable or even unsuitable for most LED lights, fluorescent lamps, electric motors. Electric motors can be dimmed but you need a slighlty more complex dimmer.

If you want to lower the power consumption investing in this circuits for only your oldfashioned light bulbs (which is about the only usable application) is counter productive. It is cheaper to replace the lightbulb with a lower rated one or even better, a LED based lightbulb.