As the interest of personal environment and health monitoring increases, various types of gas sensors are actively researched. Traditional micro-heater based gas sensors have been improved by adopting low dimensional sensing materials such as 2-dimensional (2D) materials and nanowires. New types of sensing mechanisms such as photo -activated, photovoltaic, triboelectric and piezoelectric approaches are also being reported. This paper introduces various types of nanostructure-based gas sensors in power consumption point of view and reviews recent progress of the nanostructure gas sensors by making comparisons between each type of gas sensor according to the sensing performance metrics such as gas response, sensitivity, response time, selectivity, resistance to in-terferences, manufacturing simplicity, and miniaturization.