Hybrid vehicles allow an increase in the powertrain efficiency thanks to their design. One such factor is the use of increased voltage supplying electric motors to the voltage supplying the high voltage battery. The battery voltage is increased several times in the inverter (boost) system to increase the final electric power supplied to the electric motor. The article presents the possibilities of using such a voltage boost in urban and non-urban driving conditions. The tests were performed on the latest generations of parallel hybrid drive systems in Lexus NX 300h and Toyota RAV4 hybrid vehicles. It has been shown that the boost system is used in about 30–40% of the urban drive distance (up to 20% of the driving time). The power supply voltage boost of the electric motors of both vehicles is used throughout the entire engine speed range of these machines at high torque values. Research has shown that the maximum voltage gain – approximately three times (up to 650 V) – is within the maximum torque range of the electric motors and allows for doubling the torque generated by the drive.