Nanosolar says opens German, U.S. solar plants

* Opens panel plant in Germany, cell factory in U.S.

* Says CIGS cells reach 16.4 pct efficiency

* Cuts costs for installation using larger panels

NEW YORK, Sept 9 (Reuters) - U.S. solar power company Nanosolar said on Wednesday it has opened a panel assembly factory in Germany.

It also said a U.S. cell production factory began operations earlier this year in San Jose, California.

The privately owned company, which counts as investors Google Inc (GOOG.O: Quote, Profile, Research) founders Sergey Brin and Larry Page, SAP AG (SAPG.DE: Quote, Profile, Research) founder Klaus Tschira and venture capital firm Benchmark Capital, said it is currently producing about one megawatt of cells per month.

That output will be ramped up as its moves to supply customer contracts valued at about $4.1 billion.

The panel assembly plant in Luckenwald near Berlin is a fully automated assembly factory that can produce one panel every 10 seconds, or an annual peak capacity of 640 MW when operated around the clock.

Unlike most photovoltaic companies that use polysilicon to turn sunlight into electricity, Nanosolar uses cells made of a compound of copper indium gallium selenide, or CIGS, mounted on aluminum foil that it says enables it to produce efficient cells at a low cost.