dumb defrost question

[uct]

Why can't the wasted exhaust in a dual fuel hp be used to help defrost the outside unit

[jpsmith1cm]

Do you have a system in mind or are you simply postulating an idea?

If you are running a high efficient furnace on the dual fuel system, there would be little heat left for defrost purposes.

I see the problem as being able to store the heat until defrost is required.

[VTP99]

Now if you could run both on a dual fuel setup you could pre heat the outside air. :D