`It's not that complicated.  The extra harmonic power that they are generating is then filtered out, correct?  Yes.  So the filters are dissipating a lot of heat.  No. People design the output filters of class-D amplifiers so they don't dissipate heat.  Passive electronic filters are made from 3 types of components: resistors, capacitors, and inductors. In theory, capacitors and inductors do not dissipate *any* heat  only the resistors dissipate heat.  So, people who design class-D output filters simply don't use any resistors. Only capacitors and inductors.  (In practice, real capacitors and inductors have some small amounts of ``parasitic resistance``, so class-D output filters do get slighly warmer than room temperature. Still, the total heat generated by a class-D amplifier and its filter is still far less than any linear amplifier with comparable output power.)  (So where does this ``extra harmonic power`` go, if it is not sent out to the speaker or dissipated in the output filter ? It is temporarily stored in the filter, in the capacitors and inductors. At some instants, energy flows *into* the filter, charging the capacitors and ___ing the inductors. At other instants, energy flows ``backwards`` from the filter, through the class-D amplifier, back into the power supply. This is why class-D amplifiers need a lot more/bigger capacitors on their power supply than other classes.)      `