The RHI scheme could be closed or participants face further big cuts in their payments under options for its future.
The Department for the Economy yesterday published the results of a consultation on the future of the ill-fated scheme.
Boiler owners could either face a compulsory buy-out or a substantial cut in payments.
The RHI scheme aimed to encourage people to use renewable energy. However, it effectively paid recipients for burning fuel, putting the scheme massively over budget.
At one point, it was estimated that the scheme could cost taxpayers as much as £700 million.
Officials will decide on a preferred course shortly.
The consultation document set out eight options, one of which would see a substantial cut in tariffs with boiler owners expected to pay money back to the department to recoup what is regarded as prior "overcompensation".
Another could mean scheme closure with boiler owners compensated to reflect that the 20-year term had to be cut short.
Sinn Féin assembly member Conor Murphy called for the scheme's immediate closure.
"The RHI scheme is comprehensively and irretrievably flawed and should be closed down as soon as possible," he said.
"As outlined in our response to the consultation spending more public money on a scheme that is at best ineffective and at worse counterproductive to carbon reduction is unjustifiable."
