The Victorian Government has committed to provide half-price solar batteries for 10,000 homes if it wins the November election.

The promise follows the Labor Government's $1.3-billion pledge to pay half the cost of installing solar panels on 650,000 homes over the next 10 years.

Under the scheme announced today, homeowners would be able to apply for a 50 per cent rebate on installation of a battery storage unit if they have solar panels already installed.

The scheme would be capped at $4,838 per household in the first year, before gradually reducing to $3,714 by 2026 as the cost of installing batteries is predicted to fall.

Contracts to guarantee solar, wind farm revenue

Premier Daniel Andrews also revealed the Victorian Government has signed contracts with six solar and wind farms, which he said would provide renewable power to 640,000 Victorian homes by 2020.

Solar and wind projects: Dundonnell wind farm, north-east of Warrnambool, to produce 336MW

Dundonnell wind farm, north-east of Warrnambool, to produce 336MW Berrybank wind farm, west of Geelong, to produce 180MW

Berrybank wind farm, west of Geelong, to produce 180MW Mortlake South wind farm, to produce 157.5MW

Mortlake South wind farm, to produce 157.5MW Carwarp solar farm, south of Mildura, to produce 121.6MW

Carwarp solar farm, south of Mildura, to produce 121.6MW Winton solar farm, near Benalla, to produce 98.8MW

Winton solar farm, near Benalla, to produce 98.8MW Cohuna solar farm, north-west of Echuca, to produce 34.2MW

Victoria has a legislated renewable energy target that requires 25 per cent of energy generation to come from renewable sources by 2020, and 40 per cent by 2040.

The "contracts of difference" signed with the six energy developments — some of which already have planning approval — guarantee a minimum wholesale energy price for the companies.

The Government said the six developments would produce a total of 928 megawatts by 2020, powering the 640,000 homes.

If the market rate slipped below the agreed spot price, then the Government would pay the generators the difference.

Alternatively, if the market price rose much higher than the spot price, the generators would pay the government.

The projects will generate a combined total of 928 megawatts of energy. ( Unsplash: Master Wen )

Mr Andrews said the contracts were organised by a "reverse auction", in which the renewable energy companies offered their most competitive pricing structures to the government.

"It's simple — greater supply of renewable energy means lower power prices and more jobs for Victorian families," he said.

But he said releasing the details of the contracts would risk future negotiations for other renewable energy projects.

Contracts must be public: Opposition

Opposition Leader Matthew Guy said the Government needed to tell Victorians how much taxpayer money was involved in the contracts, after Labor tabled confidential cabinet documents relating to a controversial planning decision on Phillip Island last week.

"We deserve to know exactly how much this has cost," Mr Guy said.

"So if the Government is going to hide behind 'commercial in confidence', 'cabinet in confidence', that's unique, especially given last week they were so keen to release cabinet-in-confidence documents."

Mr Guy said he was not opposed to renewable energy projects and the Coalition would release its energy policy before the election.

The Grattan Institute's director of energy, Tony Wood, said the solar battery rebates appeared to be a policy designed to buy votes, rather than good policy.

But he said reverse auctions had proven to be efficient in building renewable energy projects.

"In the absence of Commonwealth action on climate change, these are the only programs that are left," Mr Wood told ABC Radio Melbourne.

"On that basis it may not be all that financially expensive for Victorians and it may also help add to renewable energy which would have probably happened anyway if we had anything like a rational climate policy from the Commonwealth level."

Environment Victoria's chief executive, Mark Wakeham, said it was the largest clean energy auction result in Australia.

"The result stands in stark contrast to the Morrison Government's recent announcement that they have given up trying to reduce emissions and have no plan to support new renewable energy projects," he said.