Depends on the method, but you can be sure that you're losing at least 10% to inductive/RF losses, and more typically 20%.

Reasonable for a phone, batshit insane for EV charging, which is why Magne Charge never took off. (http://en.wikipedia.org/wiki/Magne_Charge) 20% of 6 kW for every car, times millions of cars...

When I had a L920, I noticed the charging plate and phone would get really hot, even after the phone is charged to 100%. Through the wire, the heat is minimal like every other phone. So, base on heat dissipation, I would say yes.