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.
HCl molecules, for example, have a dipole moment because the hydrogen atom has a slight positive charge and the chlorine atom has a slight negative charge. Because of the force of attraction between oppositely charged particles, there is a small dipole-dipole force of attraction between adjacent HCl molecules.