When works started on the Northern Territory's largest solar farm near Katherine, it was seen as a "game-changer" for the region.

But more than two years after construction finished in 2020; the solar farm is yet to generate any power.

"It's just reflecting back into space, not being used to power the grid and to substitute for diesel and gas turbine production," said local vet Peter Trembath, who leased his land to energy company Eni Australia for the solar project.

"It'll be some technical issue, but you'd reckon they would have sorted that out before Eni spent $40 million to erect it."

It's one of four Top End solar farms that have been built in the past few years but are all sitting idle and not yet supplying energy to the grid.

In addition to the 25-megawatt facility near Katherine, Eni has constructed two 10-megawatt solar farms at Batchelor and Manton.

Another company, Rimfire, also has a 10-megawatt facility at Batchelor.

A spokesperson for NT government-owned Power and Water Corporation said all four solar farms have had "electrical connections constructed and energised" and that it continued to "support these solar generators through the completion of their on-grid commissioning."

"To export power through the electrical network, generators must be compliant with the National Electricity Rules and Power and Water Network Technical Code, which ensures the reliability of power supply and power system security."

But a recent Utilities Commission of the NT report suggested the projects were taking "comparably longer to bring online" than equivalent projects in other states.

"There is a significant capacity of large-scale solar PV under test or ready to be tested that will radically change the generation mix in the Darwin‑Katherine power system," the report stated.

About 60 megawatts of available solar remains offline, or enough to power "approximately 12,000 homes," according to renewable energy expert Alan Langworthy, who chaired the Northern Territory's Roadmap to Renewables report in 2017.

The independent report outlined a pathway for the NT Government to achieve its 50 per cent renewable energy target by 2030.

Mr Langworthy said he was 'disappointed' by slow progress on many of the report's initiatives.

"What we said in that roadmap report was forget about renewables. [They] will come because they are cheaper, or they won't make the game," he said.

"But the network and the policy and administrative arrangements around the network are really not fit for purpose for the changing technology that's coming into the grid."

"There's a myriad of things that are now being used around the world to stabilise the grid, given the intermittency and variability of various sorts [of energy]."

"It's not just solar that's variable … gas, coal, solar, they're all variable inputs. Being able to manage all of that is something we really need to focus on."

Jason Fowler is an energy campaigner with the Environment Centre NT and sits on the customer advisory committee with Power and Water Corporation.

"The solar farms that have been constructed. That is a good step in the right direction," he said.

"But by not having the grid ready in time, what it has done is to provide a strong disincentive for more of these farms to be built.

"It's really up to the government to lead the way here, stop dilly-dallying around, and actually set our grid up so that we can handle a lot of solar power."

Minister for Renewables and Energy Selena Uibo said her government was committed to the Territory's 50 per cent renewables energy target.

"The four solar power stations located at Katherine, Manton and Batchelor are connected to the power grid," she said.

"Each is now progressing through the final stages of commissioning and compliance testing to ensure each power station operates in a safe, stable and predictable manner." 

"The Territory is tracking well towards achieving 50 per cent renewable energy by 2030," she said.

Peter Trembath said his contract with Eni Australia meant he received a smaller commission while the Katherine solar farm was not yet supplying power to the grid.

"To have the income from this asset, it'd be very handy," he said. 

"But I mean, it's just the fact that they're not utilising this free power – the job's done." 

"We can't go on just burning fossil fuels to turn our aircon on."

Rimfire said their Batchelor solar farm was still continuing through Power and Water Corporation's compliance and testing program, with current expectations to be online towards the end of this calendar year, "although not certain".

Eni has been contacted for comment.