Energy saving is an important issue in process industries due to the increasing cost of energy and associated environmental pollution. Retrofitting of existing Heat Exchanger Networks (HENs) is a key solution to maintain their energy efficiency and minimize utilities consumption. Several graphical methods have been developed for retrofitting design of HENs during the last few years. However, some of these methods are tedious and often leads to complex and uneconomic retrofit. This paper presents a simple graphical retrofit method to cut utility consumption of existing HENs. The new retrofitting method uses a single graph called Supply-Target Diagram (ST-D) to identify and represent potential modifications in existing HENs. A case study is used to illustrate the application of the new graphical method for a retrofitting design of an existing HEN. The addition of two exchangers using the new graphical method shows that heating and cooling utilities can be reduced by 18.75% and 40% respectively.