- "EPS systems do not require engine power to operate. Thus, a vehicle equipped with EPS may achieve an estimated improvement in fuel economy of 3% compared to the same vehicle with conventional HPS. As an added benefit, more of the engine's power is transmitted to its intended location — the wheels."
In EPS systems, the engine has to turn an alternator rather than a hydraulic pump. EPS provides fuel efficiency gains because it is more efficient than hydraulic systems, not because it is using free energy. Generally, hydraulic power steering systems are on all the time (the engine is always running the hydraulic pump) while EPS systems are on demand (only using energy when needed). There may be other efficiency comparisons between EPS and conventional PS, but it is the engine doing the work.
I suppose the only time the engine might not be operating the EPS is if the vehicle is a plug-in hybrid, but that accounts for about 0.00001% of the automotive population. LostCause 23:17, 29 September 2007 (UTC)