Accurate prediction of electronic transport properties is essential for the rational design of thermoelectric materials, particularly in complex systems where alloying, doping, and disorder strongly modify the electronic structure. While conventional transport calculations are often limited to pristine unit cells or rely on approximations that neglect local chemical environments, realistic materials frequently require a supercell-based description to capture these effects. To address this challenge, we have developed Electra, an in-house electronic transport code capable of directly calculating transport coefficients from first-principles supercell electronic structures. By explicitly incorporating the band structure modifications arising from alloying, doping, defects, and chemical disorder, Electra enables a more realistic description of carrier transport in complex materials. This approach bridges the gap between atomistic structural models and experimentally measurable transport properties, providing a powerful framework for understanding and optimizing thermoelectric performance in compositionally engineered materials.