A vehicle comprising an engine, a generator driven by the engine and configured to produce an output, a direct current (DC)-to-DC converter configured to derive a first DC voltage from the output, and a convert the first DC voltage to a second DC voltage, a wheel, an electric motor configured to receive the second DC voltage, and for driving a wheel of said vehicle drive the wheel based on the second DC voltage, and a processor configured to control the engine to run at an engine speed corresponding to a first operating point in a set of operating points, wherein the first operating point corresponds to a demanded power.