BERLIN, Aug 22 (Reuters) - E.ON, Europe's biggest operator of energy networks, on Tuesday issued 1.5 billion euros ($1.63 billion) in green bonds for pre-financing for 2024 to finance sustainable projects focused on the energy transition, it said in a statement.

The bonds were issued in two 750 million-euro tranches, one maturing in March 2029 with a coupon of 3.75% and another in August 2033 with a coupon of 4%, the company said.

The order book amounted to up to 4.3 billion euros. Bank of America Securities, Deutsche Bank, Natwest Markets and Unicredit were active bookrunners.

E.ON plans to invest a total of 33 billion euros in the energy transition by 2027 and plans to continue using green bonds as an instrument, Chief Financial Officer Marc Spieker said in the statement. ($1 = 0.9218 euro) (Reporting by Victoria Waldersee; editing by Jonathan Oatis)