Keeping coal-fired power stations open for longer, as well as encouraging new investment, will be the focus of the government’s energy policy, Treasurer Josh Frydenberg says.

Mr Frydenberg said a ‘sharp jump’ in wholesale energy prices led to the closure of South Australia’s Northern Power Station and Hazelwood in Victoria – and the government had learnt its lesson.

‘We want to see new investment but we also don’t want to see existing power generation facilities close prematurely,’ he told reporters in Canberra on Wednesday.

The treasurer said the wholesale price of power had decreased about 25 per cent through the year, and prices in South Australia, Queensland and NSW had gone down since July 1.

‘We will continue to put in place the measures that are needed to get prices down,’ Mr Frydenberg said.

‘I don’t have a lot of sympathy for the energy companies.’

Energy Minister Angus Taylor has been speaking with energy companies since laying down his plan to reduce prices, which largely focus on recommendations from the ACCC.

His plan centres on introducing a price safety net, increasing competition in the sector and stamping out price-gouging, and Prime Minister Scott Morrison has not ruled out a royal commission into energy companies.

The treasurer’s remarks come as the Northern Territory’s Chief Minister Michael Gunner told an oil and gas conference there is believed to be 400 years worth of underground gas reserves in the Territory’s Beetaloo Sub-basin.

Resources Minister Matt Canavan says estimates are yet to be firmed, but was excited at the prospect of the massive reserves.

‘The more you develop gas, the more you supply and the cheaper your energy will be,’ he told Sky News.