How much electricity does a typical home mining rig actually use?

A single CPU-only desktop mining flat out usually pulls 90-180 watts from the wall. Add one GPU and you are looking at 250-450 watts. A dedicated two-GPU rig sits at roughly 600-900 watts. Laptops are much less, often 35-90 watts even at full load. These numbers are an order of magnitude smaller than industrial ASIC operations and roughly comparable to running a desktop game for the same number of hours. The only way to know your exact figure is to measure with a plug-in energy meter; nameplate PSU wattage is the maximum the supply can deliver, not what your computer actually draws.