Input current of linear regulators
The 7812 is a linear voltage regulator and this usually means that the input current is largely determined by the output current. Input current will be a few mA higher due to the chip using current internally to power its circuits, 4mA from memory.

So if the output current is 1.000A the input current might be 1.004A.

A switching regulator is more efficient at delivering power and, for a buck regulator, the input current is usually less than the output current.