Quantum-chemical computation is a useful and widespread tool for understanding the electronic structure of conjugated polymers as well as predicting new synthetic targets. In this work, we assess the validity of considering a single conformational or structural isomer as representative of the entire conformational or structural distributions in ab-initio computations of figures-of-merit (dipole moment, HOMO, LUMO, and optical gap). It is found from surveying numerous conjugated copolymers that considering only a single conformational or structural isomer can hide significant deviations in frontier molecular orbital energies and optical gaps as well as qualitative shifts in dipole moments. We discuss the limitations of not considering isomeric dispersion on the polymer's computed electronic properties and the implications these findings have on the rational design of conjugated polymers.