Abstract Energy conservation has become one of the priorities in manufacturing industries, while the energy efficiency at process level may provide deep understanding of the energy consumption during the manufacturing process. Hot-wire laser welding of double galvanized high-strength steel DP800 has a wide range of potential applications in the automobile manufacturing field. Based on the introduction of equivalent laser power, a mathematical model was developed to obtain the energy efficiency of hot-wire laser welding. The results of theoretical calculation and experimental verification indicate that the optimum pre-heating temperature range of the welding wire in hot-wire laser welding is from 600 to 800 °C. The preheating temperature of the welding wire increases almost parabolically with the heating current. Furthermore, the developed technique can be used to realize a maximum energy savings of 16% over cold-wire laser welding. The conclusions allowed to formulate the energy efficiency evaluation as green manufacturing of novel process is concerned.