The lower vapor pressure of n-butane than gaseous fuels, such as hydrogen, methane, and propane, enables its fuel containers to be compact and highly portable. This study investigates the combustion characteristics and performance of a mesoscale annular combustor using highly portable n-butane. The inner and outer tubes of the combustor are fabricated using heat-resistant materials, and the combustion chamber has a volume of 1.84 cm3. The fuel-rich mixture and air are supplied to the combustion chamber through the inner and outer tubes, respectively. The experimental evaluation of the combustor was conducted in a region where the equivalence ratio is leaner than the stoichiometric ratio; this ratio is determined using the fuel and airflow rates provided to the combustor. The temperature of the burned gas at the combustor outlet can be varied from 1000 K to 1900 K. The combustor exhibited robust performance with maximum thermal efficiency, maximum thermal output, and energy density of 0.92, 251 W, and 137 W/cm3, respectively. The maximum pressure drop observed within the combustor (7.6 kPa) was sufficiently lower than the vapor pressure of n-butane, facilitating the supply of n-butane under its vapor pressure. Practically, this combustor can facilitate the development of portable power generators leveraging its efficient and mobile design and can be potentially used in emergency power supply systems and remote operations.