Military ground vehicles need greater electrical power generation to address continually increasing power demands due to various loads, e.g. advanced communications equipment, jamming equipment, electronic armor, and electronic weapons system. More electrical power is also required for electrification of auxiliary systems (steering, cooling fans, HVAC, and pumps) to improve system efficiency - currently driven mechanically. Electrical equipment can be powered from the 600 volt DC bus power supply or from the conventional 28 volt DC bus depending on size, cost, weight, cooling, performance, and cooling impact. Appropriate power electronics converters (dc to dc, ac to dc, dc to ac) are used to manipulate the DC source to drive equipment on the Stryker APOP electrical system. These devices are highly efficient and should lead to the reduction of parasitic losses. With the above in perspective, the US Army RDECOM-TARDEC, GVPM (Ground Vehicle Power and Mobility) has been pursuing the APOP (Advanced Propulsion with On-Board Power) project which is being implemented in the Stryker vehicle. This paper describes the effort related to modeling and simulation (M&S) in order to study the effect of having the higher power generator and the engine, together with the newly introduced electrical loads in the APOP vehicle and how the overall vehicle behavior is impacted.