The Coalition is claiming significant savings from its plan to scrap the government's $10bn clean energy financing fund, but budget documents show the fund is paying its own way and the abolition would deliver only tiny savings.

The shadow treasurer, Joe Hockey, twice mentioned the fund during media interviews on Wednesday morning as an example of significant savings the Coalition had already announced, as he explained that the remainder of the costed savings and spending plans would be released "in good time" before the election.

"We are dealing with everything in a measured way," Hockey said in an interview on ABC radio's Breakfast Show. "We already made a number of announcements – for example we said we are getting rid of the $10bn Clean Energy Finance Corporation, we have said we are cutting the refugee intake from 20,000 to 13,750, which saves $1.3bn, we are getting rid of waste like the $180,000 on ergonomic chair studies in one department, so we have already made a number of announcements which Labor tends to ignore."

But since the corporation lends money at commercial rates it is actually "off-budget", because it expects to earn a return on its investments.

When it was originally announced in 2011, a cost of $944m for its first four years was shown in budget documents on the assumption that that the CEFC would finance some projects on a concessional basis and that a small proportion of its loans would not be repaid.

In costings provided along with his budget-in-reply speech, the opposition leader, Tony Abbott, appeared to be relying on this information when he claimed savings of about $350m to $450m a year from abolishing the corporation.

But after the corporation's board was established, it decided to take a very cautious approach to its financing and lending which meant that cost was removed from this year's budget and is no longer available as a saving.

The tougher lending criteria were specifically mentioned in an email from CEFC chief executive Oliver Yates to the Coalition, which was published in the Australian newspaper in May. The email said the CEFC would operate commercially and would not make grants or risky loans.

"The making of such are inconsistent with the approach of being self-sustaining and commercial," Yates reportedly wrote.

In this year's budget the CEFC costs only $18m in start-up costs in each of the first three years – suggesting there would be almost no savings from its abolition.

The Coalition's plan to repeal the carbon tax will cost close to $10bn and its plan to repeal the mining tax another $3.7bn over the next four years. It is also going to cut the company tax rate, which will cost $5bn over the four-year forward estimates and it won't proceed with the government's crackdown on fringe benefit tax breaks for company cars. It is also proceeding with expensive spending plans, including the paid parental leave scheme.

It has announced some savings in addition to those mentioned by Hockey, including $1.75bn from cutting the public service, discontinuing the government's contribution to low income earners' superannuation to save just under $1bn a year and delaying the phased increase in compulsory superannuation from 9 to 12%, so that the 12% increase is achieved in 2021 rather than 2019, to save around $1.1bn a year by 2016-17.

The Coalition has also said it will abolish Labor's schoolkids bonus, which saves around $1.2bn year.

Hockey says all these policies are being costed by the parliamentary budget office and will be released "in good time" before the election. He promises the savings measures will exceed the spending measures, and says this means the budget bottom line will always be better under the Coalition. But Hockey repeated that he will not be bound to any projected deficit or surplus on the basis of the election costings, because this would have to use the recently released treasury figures as its starting point.

The prime minister, Kevin Rudd, claims Abbott "plainly has a hidden plan on his cuts to education and health" which he did not want to reveal because "if the Australian people knew what it was they'd be very, very worried about voting for him".