Tender documents have revealed the first stage of the $150 million scheme will likely be restricted to just households, as part of a phased rollout.

It comes as new figures revealed more than 3500 Canberrans have already expressed interest in the scheme, where the government provide interest-free loans for residents to purchase items such as rooftop solar panels, battery storage systems or electric cars.

It's expected Canberra businesses or community organisations will be able to participate in future phases of the scheme, once the first stage starts in the second half of 2021.

They are, however, able to express interest in signing on to the scheme.

An official start date for the initiative is yet to be confirmed.

"The territory is considering a phased implementation process, this will enable testing key aspects of the program's design including commercial arrangements, risk mitigation measures and customer demands, to help refine the design of the full loans program before it is rolled out across the territory," the documents said.

While the total amount allocated for the scheme has been set at $150 million, there will be $30 million set aside for the first phase.

Individuals will be entitled to interest-free loans of between $2000 and $15,000, which will be repaid over a 10-year period.

Since the scheme was launched in March, more than 3500 people registered an expression of interest in the initiative.

Of those, 75 per cent have registered for a loan for rooftop solar panels, while 65 per cent of applicants expressed interest in battery storage.

Those who have registered have been able to express interest in more than one product.

Changing over to electric heating or cooling from gas was the next most popular product, with 40 per cent expressing interest, followed by changing over hot water heat pumps at 35 per cent, electric vehicles at 30 per cent and converting gas appliances to electric ones had 20 per cent of applicants interested.

An ACT government spokesman said 15 installers or suppliers had put up their hand to be a part of the scheme once it gets under way.

Chief Minister Andrew Barr said at an estimates hearing in March that he did not expect a rush of people to join the scheme straight away after it launched.

He said the scheme would be aimed at middle-income households.

"It's not the government's intention to help multimillion-dollar homes make the switch, it's very much a middle Canberra program," he said.

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"It's very much about those who ... understand they need to make the change, but can't afford the upfront cost."

Businesses looking to sign on as a provider for the scheme were likely to be established players in the market, as opposed to new start-ups, the Chief Minister said.

"It will only be approved and accredited suppliers, we're not looking to attract new entrants and there'll be no cowboys," he said.

"It's very much a sustainable path for an industry that's growing substantially."

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