Why does welding use more energy than the amount needed to form a joint?

In all welding processes, the total energy input exceeds the amount strictly required to form a joint because not all generated heat can be effectively utilized for the weld itself.1

The primary reasons for this energy discrepancy include:

• Heat Loss: Significant amounts of heat are lost to the surrounding environment through radiation and by conduction through the base metal.1
• Process Efficiency: Depending on the specific welding method, thermal efficiencies typically range between 60 and 90 percent, meaning a portion of the energy is inherently dissipated rather than applied to the fusion zone.1

Because of these factors, the heat source must generate enough energy to maintain a molten pool of the required size while accounting for these unavoidable losses.1