Hello newbie here,

I got a raspberry pi 4 and an old tv monitor and I wanted to construct a magic mirror.
Before I get started I’d like to know how much I’m gonna have to pay for leaving it on.
I don’t know if I can turn off the tv screen with the pi, so there’s that.

Is there any easy way that I can measure this, btw I have no clue when it comes to mAh or watts or energy bills, or whatever is needed.

A clear video explanation is preferred instead of a textual guide :)