We present self-consistent quantum transport calculations for device structures based on metallic and semiconducting carbon nanotubes. We combine the non-equilibrium Green's function formalism with an extended Hückel Hamiltonian and a Poisson solver for a realistic representation of the device and contacts’ chemistry and the system's electrostatics. We consider pure nanotubes and Au, Pd and Al metallic electrodes and reflect on their transparency in terms of non-equilibrium charging effects. Our attention focuses on the variations of the system's transport features when tuning the terminal potentials, which represent the external parameters of our semiempirical model. Results reveal a non-generalized dependence of the conduction mechanism on helicity, electrode type and bias factors. We finally demonstrate that self-consistency is essential for quantum transport calculations of semiconducting carbon …