Did a little searching since my electronics theory is a bit rusty, if I remember correctly is the current in is the same as current out on a linear. I found this info:
A Switching converter for 12v in to 5v out @ 1.5 A peak current looks about 91% efficient. If it's supplying 7.5 W at 91% efficiency, it would be wasting 0.7 W from itself.
A linear regulator dropping 12 V to 5 V at 1.5 A would waste 10.5 W while supplying 7.5 W, making it 42% efficient.