With the introduction of the new HS250h, Lexus brings forth the first dedicated luxury hybrid. In the process it's also expanding the electrification of ancillary components. Ever since the original Prius, hybrid engineers have been replacing mechanically driven systems with electrically driven equivalents. For example, components like hydraulic power steering pumps are replaced by electric versions, as are air conditioning systems. This is partly to ensure that these systems continue to function when the engine has been shut off and electric drive is active.
These electric systems are also more efficient and can be controlled to provide their functions on demand, thus reducing parasitic losses from driving them continuously. The latest addition to this electrified drive lineup is the transmission oil pump on the HS250h. The oil now also flows over the electric drive motor, improving its efficiency. The new electric pump is actually the second on Toyota's new for 2010 hybrids. The new Prius and HS250h both feature electric water pumps as well.