Scale builds up on the heating elements because it precipitates out when the water turns briefly to gas. Once present, the scale will negatively impact the coef

Scale builds up on the heating elements because it precipitates out when the water turns briefly to gas. Once present, the scale will negatively impact the coefficient of heat transfer between the element and the water. A microwave system wouldn't have any heating elements, and any precipitates would fall harmlessly to the bottom, not hurting efficiency.