The two instalments of $75 will extend an initial $300 energy bill rebate until the end of 2025 and will automatically be applied to household and small businesses' energy bills from July 1.
The pre-election sweetener will cost about $1.8 million and forms the centre-piece of Labor's pre-election budget, which will be handed down on Tuesday.
"This is cost of living relief when it's needed right across the country," the Prime Minister Anthony Albanese told reporters in Sydney on Sunday.
Labor's fourth budget will return to the red after Labor posted two surpluses but the deficit is lower than predicted in previous budgets.
Mr Albanese didn't respond on why the rebate was only extended to the end of the election year and didn't commit to extending rebates into 2026.
"What we've seen is that in 2024, power prices fell 25.2 per cent, they would have fallen just 1.6 per cent without rebates," he said.
"So this is energy bill relief, cost-of-living support that will also have an effect of putting downward pressure on inflation."
The rebate would slash household bills by an average of 7.5 per cent and bring down inflation by half a per cent, according to Treasury estimates cited by the federal government.
Electricity prices are set to rise from mid-year, with the Australian Energy Regulator recommending an 8.9 per cent increase to the maximum amount customers can be charged in certain parts of the country.
The coalition will support the rebate, locking it in no matter who wins the election, which will be held in May.
The rebates showed Labor had a failed energy policy as rebates were needed to artificially decrease power bills, opposition finance spokeswoman Jane Hume said.
"Do you remember three years ago, Anthony Albanese said 97 times that he was going to bring down energy prices by $275? Well he's failed," she told Sky News.
"We will not stand in the way of that energy relief but the aim has got to be to sustainably bring down energy prices."
Senator Hume called for more gas to be pumped into the energy grid and the life of aging coal plants to be extended to bring down prices in the short term, until nuclear power plants could be brought on in the late 2030s and 2040s.
The coalition's plan to bring seven nuclear plants online has been criticised by experts and Labor for taking too long to fire up and too expensive to run.
Australia's abundance of wind and solar resources makes those forms of renewable energy cheapest, they say.
The coalition plan is set to cost taxpayers $330 billion and would still be propped up by renewable energy but the opposition argues it will be hundreds of billions of dollars cheaper than Labor's primarily renewable energy plan.
Opposition Leader Peter Dutton will deliver his budget reply speech on Thursday and is under pressure to announce a key election pledge ahead of a campaign after the Liberals lost momentum as Labor clawed back ground in the polls.
The most recent YouGov polling showed the two major parties are neck and neck ahead of the federal election and are tied on a two-party preferred basis.
Labor has gained ground in outer-metropolitan electorates but trailed the opposition 36 per cent to 35 per cent in outer suburbs.
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