Even a new, minimum efficiency air conditioner or furnace can be a significant jump in efficiency. The old furnace in your basement may only be originally rated at 60% to 70% AFUE. In order to comply with national regulations, furnaces manufactured today have to be rated at a minimum of 80% AFUE.
dipole - a pair of equal and opposite electric charges or magnetic poles separated by a small distance. couple - (physics) something joined by two equal and opposite forces that act along parallel lines. electric dipole, electric doublet - a dipole with equal and opposite electric charges.
dipole (two pole) is due to existence of PARTIAL positive or negative charge. This charge is due to difference in electro negativity and this charge is represented by DELTA symbol. So the dipole dipole interaction is much less than an ion-ion interaction (in terms of strength).