The prototype has been installed on a precast concrete tower with a hub height of 135 metres in northern Germany.
The new turbine is based on Enercon's E101 3MW, but has been fitted with newly-designed segmented rotor blades for transport.
When Windpower Monthly originally reported the development of the E115 in September last year, it was proposed as a 2.5MW low-wind machine.
The turbine is also available with hub heights of 92-149 metres, with the latter configuration offering a total installation height of 206.5 metres.
Enercon said that at average wind speeds of 6.5m/s at 149 metres hub height, the E-115 can generate an annual output of roughly 9.3 million kWh. This is an increase of 14% on the E-101's output.
Serial production of the new turbine will begin in mid 2014.
Enercon has been focusing on low- to medium-wind turbines recently, despite many of its competitors developing products for the offshore market. In May, it targeted the medium-wind market with the E-92.