The goal of this paper is to explore the complete set of single mode hybrid electric powertrain designs that can be generated with one and two planetary gearsets (PGs). Contrary to an automated design exploration approach, an analytically-based manual method is developed to identify all unique design modes for each hybrid electric powertrain architecture (parallel, series, power-split) that can be created with two planetary gearsets, one engine, one vehicle output shaft, two electric machines, and at most two brake clutches. Feasible design modes are generated according to a procedure that provably covers the entire design space. The procedure systematically creates all feasible combinations according to the number of connections between PGs; the number of brake clutches; whether brake clutches, vehicle output shaft, and engine are connected to the nodes that combine two PGs; whether engine and vehicle output shaft are connected to the same PG; whether they are connected to the PG with brake clutches and whether electric machines are collocated with the engine and/or vehicle output shaft. The results of this approach not only show the number of unique design modes for each hybrid electric vehicle architecture and their torque and speed relationships, but also provide a means to validate the results obtained through automated design mode exploration methods.