What is the maximum wattage/amperage the Magic Mouse 2 can consume? Oddly I have to charge these things a lot and I'm trying to determine which power of AC-USB charger to buy without being wasteful. 

For example, if I use a 12W (2.4 amp) iPad charger, will the magic mouse consume all 12W, or will it use a stepped-down trickle like 2.5 watts from the 12 watt charger?

Apple doesn't seem to list this info anywhere.
Using a USB voltmeter (at @n1000's recommendation), this is the Magic Mouse 2 consumption rounded to the nearest 10th:

0.5 Amps (2.5 Watts) while switched off



1.5 Amps (7.5 Watts) while switch on