Abstract The concept of heat exchanger efficiency eliminates the need for charts, or complicated performance expressions, providing a convenient approach for solving heat exchanger rating, and sizing problems, as well as network of heat exchangers. The efficiency of all heat exchangers is determined from a single algebraic expression. This paper is comprehensive, and streamlined presentation of the approach. It also provides a new expression for solving sizing problems, provides a closed form expression for determining the minimum number of heat exchangers needed when one cannot meet the design specifications, presents a new methodology for analyzing network of heat exchangers connected in series, and provides closed form expressions for determining the size and the rate of heat transfer in individual heat exchangers of a network.