The substation, on Queenstown Hill, will be operated by Delta.
It took 16 months to complete and houses two transformers and switchgear.
It would ensure the resort's electricity distribution network maintained a high level of supply security over the next 20 years.
Aurora Energy chairman Ray Polson said Queenstown had experienced at least 3% growth in electricity demand annually over the past five years.
"The new substation provides greater network supply security for 1600 Queenstown homes and businesses and is the single largest investment in a substation ever completed by Aurora Energy.
"[It] is part of the company's wider infrastructure investment programme in the Queenstown Lakes district, including projects already under way to increase electrical capacity for the Frankton and Cardrona areas.
"Once completed, these projects will see electrical capacity increase by around 40%, future-proofing the region's electricity supply for the benefit of everyone who lives and works here," Mr Polson said.
Delta chief executive Grady Cameron congratulated the contractors involved for completing the project on time, within budget and safely.
"The substation design incorporates a number of environmental innovations.
"With care and forethought, the project demonstrates how key infrastructure can be developed in harmony with the surrounding environment, preserving values important to the community," Mr Cameron said.
