The energy minister Angus Taylor has backed Malcolm Turnbull’s pet project, the expansion of the Snowy Hydro scheme, ahead of critical deliberations on the project due next month.

Taylor will use a speech on Wednesday to express confidence that Snowy “will be a fundamental part of our future energy needs for many generations”. The board is due to decide in mid-December whether to proceed with additional generation capacity of 2,000MW.

In affirming the project’s contribution to Australia’s energy mix, the energy minister will highlight his family connections to the scheme. Taylor’s grandfather was the chief engineer and commissioner for the original post-war Snowy project.

According to the speech distributed in advance, Taylor will say that as Australia moves into “a new reality for energy the Snowy region will play an even more important part in supporting our nation in the future”.

He will say Snowy’s place in Australia’s energy mix becomes more important as intermittent generation becomes more a feature of the electricity system, because the scheme “has unrivaled capacity to store power when it is not needed, and generate it when it is needed”.

“While gas and batteries both have an important role to play, pumped hydro provides relatively low-cost storage and can run for extended time frames to match volatile supply with volatile demand,” Taylor says.

“Put simply, we need to effectively firm that generation, providing solution for when the sun isn’t shining and the wind isn’t blowing, and that will matter most when we face solar and wind droughts.”

He says pumped hydro is superior to batteries “because they can’t store enough power at a sensible cost” and gas can’t store power at all.

Taylor will note that the proposed expansion, adding 2,000MW to the hydro scheme’s 4,100MW capacity – enough to power 500,000 homes – has not yet reached financial close “and the business case must stack up”.

“But I am confident that projects like Snowy will be a fundamental part of our future energy needs for many generations.”

When the expansion was first announced by Turnbull last March the cost was estimated at $2bn. But a range of experts have pointed out that fails to take into account the construction of additional infrastructure, like poles and wires, to transmit the power – which could add another $2bn to the cost of the project.

As well as determining the future of the Snowy project, Taylor will also attempt in December to secure agreement from the states to implement to reliability component of the otherwise abandoned national energy guarantee.

The Morrison government has dumped the emissions reduction component of the Neg but is continuing the press the states to adopt the reliability obligation of the policy, which requires retailers to supply sufficient quantities of dispatchable power to the grid.

Taylor will say securing the reliability obligation is “one of the highest priorities for the commonwealth”. It has been unable to proceed with striking agreement in part because the Victorian government is currently in caretaker mode for the state election.