The electronic properties of carbon nanotubes (CNTs) play an important role in their electrochemical performance for energy storage devices such as supercapacitors and batteries. Information such as charge transport, charge density and band energy diagram are required to fully understand electronic behavior of CNTs in electrochemical devices. This study investigated the charge transport in carbon nanotube thin films using conductive atomic force microscopy (C-AFM) and scanning Kelvin probe microscopy (SKPM). Freestanding single-wall carbon nanotube (SWCNT) films of about 1 um in thickness were prepared using a simple casting method. Transmission electron microscope images and Raman analysis indicate very low amount of amorphous carbon (<1%) and majority of the tubes are metallic type. Specific capacitance of SWCNT supercapacitors is ~ 8mF/cm2 or 276 F/g, which is comparable with prior reports. C-AFM data reveal that resistance of bundles of SWCNT is in the range of several MW. The CNT films switch from resistance behavior to capacitance behavior when about 35% volume of it becomes conductive. SKPM images show that work function of CNTs depends on diameter of CNT bundles, meaning the size of CNT bundles regulates the charge and discharge performance of supercapacitors.