Is power being used on the following products?

Question

I have phone chargers and laptop chargers and im wondering if they are using any electricity. The laptop charger has a led light so i think it must use power. But phone chargers plugged in with out charging a phone? And also my stero system is on standby with an led but is that using electricity also ?

Answer 1

A transformer uses power whether the load it's providing to is on or not. Multiply the input voltage by the input current and this is the power consumed. Power to load is drawn from the secondary winding.

Answer 2

The laptop charger definitely is

The phone chargers probably aren't

and the stereo system on standby is (more then you think)