Abstract: A power generating system wherein a turbine (34) is mounted on top of a tower (30) or tethered underwater. The turbine (34) includes a rotor having a main blade (20) connected to a rotor hub (40) and an extender blade tip (22, 22?) attached to the main blade (20). During manufacture, the optimum energy-capture is determined using site-specific conditions of one or more of air density, wind speed, extreme wind, wind shear, noise and turbulence intensity. The extender blade tip (22, 22?) is chosen from a number of extender blade tips having a length that is the closest to the determined optimum energy-capture. The chosen extender blade tip is attached to the main blade either during manufacture or on-site. Alternatively, a one piece blade is produced based on information determined from the site specific conditions. The tip of such one piece blade can be customized based on the information obtained.