Another 36 turbines are about to be added to the Kaiwera Downs wind farm near Gore, which already has 10 working turbines.
The beginning of the second stage of the $486million wind farm project was marked with a ceremony yesterday.
Mercury chief executive Vince Hawksworth said it was "fantastic" to start stage two of the project.
"It’s been a long time in the making."
With the level of water in some hydro-powered lakes low at present, wind power was a viable option for the future, he said.
"The reality is that it is very difficult to do more hydro.
"It is much easier to do wind projects.
"They’re quicker to do."
Wind was "reasonably" predictable over the long term.
"As soon as those turbines start spinning they start producing electricity ... you build a hydro system, you don’t even start producing until the whole thing is completed."
He acknowledged hydro was still an important energy source due to its ability to be stored.
The new turbines, which were southeast of the first stage, were about 15m higher than the existing turbines because of the geography.
Mercury executive general manager portfolio Phil Gibson said a couple of hundred people would be working at the site during its peak.
"[The number will] come and go from time to time as the project goes through different stages."
Turbines would begin to be erected in 16 months, he said.
Gore district councillor Joe Stringer commended Mercury’s multimillion-dollar commitment to the district.
"This is an incredible milestone that Mercury has achieved here.
"Great to see that stage two is now under way."
