Resistance spot welding (RWS) guns driven by servomotors instead of pneumatic cylinders are called servo guns. They bring many new features to RWS process. In this study, the influences of servo guns on RSW process are systematically investigated based on comparative experiments. In addition, the costs of servo guns are also analyzed. The long-term applications of servo guns will be cost effective due to their technical features and savings on pneumatic systems although the acquisition cost of servo guns is high. Therefore, servo gun is an excellent alternative RSW machine for sheet metal assembly.