UTV can reveal that around £420m originally available to fund the Renewable Heat Incentive scheme in Northern Ireland will not be spent under current plans.
In fact, the pot of money available for green energy schemes in Northern Ireland which could go unspent could be as much as £660m.
The details have been obtained in a Freedom of Information request made to the Department for the Economy by the Renewable Heat Association of Northern Ireland.
The controversial green energy scheme is widely viewed as one of the key factors in contributing to the collapse of Stormont in 2017.
It was set up to encourage businesses to install biomass boilers as an alternative to gas.
Those who signed up were offered tariff payments from the government for 20 years. But when it was discovered the scheme was set up to be too generous and effectively encouraged the burning of energy, it was suspended.
At the time it was estimated the 20-year cost of RHI could reach £700m.
In response to a question from the association which represents boiler owners who are on the RHI scheme, the department states: “The forecast level of underspend in AME for the period 2021-36 at current budget levels is expected to be in the region of £420m.
"There are currently no plans to extend the NI RHI Scheme beyond 2036 and all eventual budgets will be dependent on future Spending Reviews."
However, the Renewable Heat Association believes the figure is likely to be significantly more as a similar scheme in England has been extended for six more years, meaning the NI Executive could access more funds too.
RHANI predicts the underspend is at least £660 million, very close to the original estimate of overspend.
The chair of RHANI Andrew Trimble said: “If civil servants had not removed 107 words from the national legislation on renewable heat when the NI legislation was implemented, then, today we would have a strong, sustainable, environmentally friendly renewable heat sector contributing to our pathway to net zero, a vastly reduced reliance on fossil fuels – with their polluting emissions reduced by 7%."
Boiler owners have gone to court to challenge the cuts in tariffs handed to them by the department over the last number of years. It has been complicated and slow.
In the FOI response the department also states: “The department will explore the potential to utilise any available AME funds in support of alternative or additional actions to decarbonise heat."
But no other green energy scheme was supported by the Executive before it collapsed and so the money isn’t being used.
The AME funding made available for the RHI scheme has come from Westminster.
During the inquiry into the failings of RHI in Northern Ireland a senior civil servant revealed that a DUP adviser said “we can fill our boots” because the Treasury was picking up the bill.
It is a view that was heavily criticised during the inquiry hearings, that just because someone else was paying shouldn’t mean all the money should be spent.
Since the suspension of the scheme the tariff payments to the 1,990 boiler owners have been significantly reduced, meaning all the money available for the scheme is now not being utilised.
The loss of public confidence in the RHI scheme and because of how toxic it became politically has made it difficult for a happy balance in spending to be found.
The political parties at Stormont committed to closing the scheme completely as part of the New Decade, New Approach deal to resurrect the Executive and assembly in 2020.
However, no progress was made on that before the latest Executive collapse, triggered by the resignation of the DUP first minister.
The Economy Minister Gordon Lyons told reporters two weeks ago that he had tried to bring a paper on the future of the scheme to other ministers, but was blocked from doing so.
Sinn Féin, however, claimed Mr Lyons paper proposed increasing tariff payments to boiler owners and accused the DUP of stalling on the closure of the scheme.
Instead the scheme will continue in its current form for now.
It cost £2.9m during 2020-2021, while £33.47m was available from Westminster.