Power Supply

I would like to power my arduino uno r3 off external power with 5v but i am not sure how many mw it should be?

I would like to power my arduino uno r3 off external power with 5v but i am not sure how many mw it should be?

By itself, the Arduino draws very little current. Even a wimpy 9V battery can power it for quite a while.

If the Arduino has things attached, like a LCD or a GSM or Ethernet shield. the power consumption can go way up.