Makani is based at former naval base, Almeda Point, which is located in the East Bay, California.
The acquisition is the first major move for Makani since Google X, the secretive research and development division of the multinational internet giant, after it acquired the firm in June 2013.
Google has backed Makani to the tune of $15 million over the past seven years, and a full takeover became more likely after the death last October of Makani's founder and design team leader, Corwin Hardham.
Makani completed the first fully autonomous flight of a 30kW kite power system, the M30, in May 2013. Work has also begun on a three-year programme to design, test and commercialise a 600kW version, dubbed the M600.
High-altitude wind is being pursued by a number of start-ups employing different turbine designs. The companies include Windlift of North Carolina, which has backing from the US defence department.