However, Aurora chief executive Grady Cameron has defended the decision to use council-owned infrastructure company Delta as a preferred provider for irrigation connections to Aurora's electricity network.
Delta was already responsible for managing Aurora's network, and the two companies shared the same management and board directors.
The change would cover work on all irrigation connections to Aurora's electricity network in an area stretching from Hawea to Millers Flat.
Mr Cameron - the chief executive of both Aurora and Delta - said the change aimed to avoid ''piecemeal'' planning for future growth in irrigation demand in the area, and the potential for ''unnecessary'' price hikes for consumers.
His comments came in a letter confirming the change sent to affected parties by Mr Cameron on December 19.
Mr Cameron, who was not available for further comment on Tuesday, said in his letter the change was driven by the ''very rapid growth'' in demand for irrigation in Central Otago.
The company wanted a co-ordinated approach as it planned for that growth, he said.
It had already committed to a $9.8 million upgrade of its transmission network, and expected that investment could nearly double over time, to meet rising demand for irrigation in the area, he said.
''Proper oversight of network planning and development activities avoids piecemeal solutions and inefficient investments by Aurora that could lead to unnecessary increased charges to electricity consumers,'' he said.
Network Electrical Servicing Ltd director Michael Fife told the Otago Daily Times the change meant an uncertain future for some of his company's staff.
His company had previously secured some of the work, and recently employed two new workers in Central Otago, doubling staff numbers to four, in anticipation of extra irrigation work.
Aurora's decision had come as a ''shock'' and meant the workers' futures were uncertain once existing work was finished, he said.
''They're shutting us out of the picture. It's some of the work that we were actually doing at the time.
''We've got outstanding work to carry on with for another three or four months, but after that I'm not too sure.''
Peak Power Services managing director Murray Popenhagen, of Queenstown, also confirmed ''something was in the wind'' and his company was also potentially affected. He would discuss Aurora's decision with the company, and declined further comment until after he had done so.
Mr Fife told the ODT he was also concerned Aurora's change would put an end to competitive market pricing for the irrigation connection work.
''If you're going to have one contractor doing that kind of work, how is competitive market pricing going to be available to the consumer? Because really it's going to only be one company doing that work, and no-one else will be able to do it, so the consumer out there is only going to get one price.''
He had raised his concerns in a letter to Mr Cameron on Monday, who responded the same day by saying there would be some ''compromise'' to market pricing as a result of the change.
The long-term benefits of optimal infrastructure development were believed to outweigh those of competitive pricing, ''if indeed such [benefits] actually exist'', he wrote.
It would also remain be ''business as usual'' for Mr Fife's company - at least for now - for irrigation connections to other parts of the network, Mr Cameron said.
However, that could change in future, as Aurora regularly reviewed its procurement policies and ''cannot give any guarantee that other connection work will remain unchanged over time'', he wrote.
Mr Cameron, in his December 19 letter, also signalled work on other types of connections to the Aurora network - including ''general development - could also fall under Delta's exclusive umbrella in future.
