This paper presents a general, practical and operational methodology to improve energy efficiency of processes through a holistic approach. The required methods and tools have been developed based on a systemic approach of process energy integration and energy efficiency optimization. The objective is to develop a general methodology adaptable to any type of industrial chemical process, existing and under development. This methodology consists of six steps: 1. The development of a process flowsheet and determination of material and energy balances, 2. Definition of the heat requirement of the process and establishment of the composite curves, 3. Calculation of the maximum energy recovery using the pinch method and statement of an ideal target, 4. Proposal of technical improvement solutions through process energy integration, modification of the process operation units -incremental and/or step changes-, 5. Selection of the most promising solutions, evaluation of the investment costs, and designing of the heat exchangers network and 6. Evaluation of the profitability of the most promising proposals and choice of the best compromise. The application of the proposed methodology is demonstrated through the case study highlighting the different steps and the potential of this approach.