New Seneca rooftop ACs...

I understand how it works. Just wonder whether it's a better option to use the electricity to run the heat pump versus the propane to run the furnace. Does the heat pump send the warmed air through the A/C ducts like the A/C would? The furnace ducts come out on the floor... what about the heat pump?

I can see the obvious benefit with a night or two plugged in, but how about when electricity is metered?