A.O. Smith Corporation is an American manufacturer of tankless water heaters with more than a century of experience in residential and commercial heating products. The company’s main factory unit in Tennessee is the world’s largest of the kind, while A.O. Smith’s products are the most widely used in the American market. The tankless water heating units available in A.O. Smith’s range cover every need with quality solutions that can serve to up to ten gallons of hot water per minute at an energy efficiency level of above 80%. Indicative of this quality is the 15 year warranty for all tankless heaters built by A.O. Smith.