Abstract: An offshore windpower plant (OWP) including a wind turbine and foundation and a new method of installing them that exclude the use of a jack up crane vessel. By this system and method, named OWP technology, the completely assembled wind turbines are lifted from the shore stand, using the buoyancy force of a catamaran wind installer (CWTI), transported to the preinstalled foundation, engaged with it in a manner that would exclude CWTI from rolling and pitching and by this allow to use the installed foundation as the base for stability for safely placing a wind turbine on it allowing placement of wind turbines on foundations regardless of the depth of their installation. The CWTI does not need a heavy lift revolving heavy lift crane and also does not need legs, thus making the system and method simpler, smaller and drastically less expensive than jack up crane vessles.