SSE is investing £100 million (€114 million) in a giant hydro scheme which would double the UK's ability to store energy for long periods.
The 92m-high dam and two reservoirs at Coire Glas in the Highlands will be Britain's biggest hydroelectric project for 40 years, the BBC reported.
Scottish ministers approved the 1.5GW pumped storage facility in 2020.
SSE wants assurances from the UK government before finally signing it off.
A spokesperson for the Department for Energy Security and Net Zero said it was "committed to supporting the low carbon hydro sector, including hydro storage".
Perth-based SSE added that the scheme would help tackle climate change and improve UK energy security.
The scheme involves two reservoirs at different heights in the Great Glen and water would be pumped 500 metres uphill for storage in an upper reservoir with the capacity of 11,000 Olympic-sized swimming pools.
When supply is tight and prices high, it would be released, using gravity to generate electricity by spinning four turbines below on the banks of Loch Lochy, before flowing into the lower reservoir.
Coire Glas could help smooth the transition from oil, gas and coal to more sustainable but intermittent sources of energy such as wind and solar.
"We believe strongly it could play a huge role in enabling a decarbonised energy system," said Finlay McCutcheon, SSE's director of onshore renewables.
Keith Bell, professor of future power systems at Strathclyde University, said the proposed scheme would also help with another policy objective - reducing the UK's reliance on imported gas, a challenge given added urgency by the invasion of Ukraine last year by the world's largest gas exporter, Russia.
SSE outlines plans for UK’s biggest hydro scheme
