[ICanHas]

Don't forget the indirect losses. Dryer is similar to a single vent portable A/C. There's been some laboratory testing done on portable ACs and many have been found to have a negative efficiency when they factored in heat gain through infiltration of outdoor air into the house for make up air.

If it's in the conditioned space and it's in the summer, you would open a nearest window and run it at night/early morning when bringing in outside air is not objectionable humidity and temperature wise so you avoid drawing a negative pressure and pulling in warm attic air into the hose.

If you run it in middle of the day, most of heat generated by the dryer goes out the vent, but the dryer is pumping out conditioned air and your A/C has to re-condition make-up air, that is drawn in as the dryer exhausts air conditioned air.