A Bréguet Range Equation for a hybrid-electric (thrust-rated) jet aircraft was formulated by modifying the conventional Bréguet Range Equation derivation to incorporate a power-rated electric motor and battery energy source. The resulting ranges for conceptual hybrid-electric aircraft were compared to a hybrid-electric flight performance simulation using publicly available aircraft data for the Embraer ERJ-175 regional jet aircraft. Various degrees of hybridization were simulated with the time-stepping flight performance model and compared to the Hybrid-Electric Bréguet Range Equation (HEBRE) results. It is shown that the HEBRE and the time stepping model produce highly consistent maximum ranges across various levels of hybridization and battery specific energy values. Additionally, range values obtained by the HEBRE across a span of flight Mach numbers were consistent with those produced by conventional and fully-electric variants of the Bréguet Range Equation, when simulations were conducted at the limits of zero and 100% hybridization factor. Results obtained from the time-stepping model and the HEBRE also indicated similar cruise Mach numbers for maximum range across a series of hybridization factors. These results demonstrated that, as the degree of hybridization in the power system increases, the cruise Mach number for maximum achievable range decreases.