'Get through tonight': NSW to save energy

Residents of NSW have been urged to reduce their energy usage in the coming hours as a number of coal-fired power stations unexpectedly failed to come offline, despite intervention by the electricity market operator.

NSW Treasurer and Energy Minister Matt Kean told media on Wednesday night people should limit their electricity usage between 5.30pm and 8.30pm if safe to do so, as the government looked to "get through tonight and the next couple of days".

"Perhaps not using the dishwasher until we go to bed, that would help," Mr Kean said.

"This is a result of a number of our coal-fired power stations not working when we need them to do so.

"What we're doing is focused on making sure that we get through tonight and the next couple of days."

His comments come after the national electricity market was suspended on Wednesday, as the Australian Energy Market Operator (AEMO) said it had become impossible to operate within the rules.

AEMO said in a note it had suspended the electricity spot market in NSW, Queensland, South Australia, Tasmania and Victoria until further notice.

It is the first suspension since the national energy market began in 1998, and gives the operator control of direction of supplies from generators to the grid along the east coast and will set power prices for all states.

"We're working very closely with the Australian Energy Market Operator to make sure that the system remains reliable," Mr Kean said.

Mr Kean said he was not aware of why the coal-fired plants had not come online, adding the situation was evolving.

"These are ageing bits of equipment, they are obviously less and less reliable.

"What we need to see is those plants caught online as soon as possible."

Mr Kean said the VIVID light show would continue throughout the Sydney CBD, Circular Quay and Darling Harbour, but he said the government was looking at options to reduce energy consumption.