But a legal challenge has also been lodged on behalf of NSW consumers by the Public Interest Advocacy Centre (PIAC), which says the revenue cuts - and therefore savings to electricity users - should be larger.

The announcements follow a ruling by the Australian Energy Regulator last month which sliced about 20 per cent from the revenues of the businesses over the next four years.

The challenges could also affect the amount the NSW government might get for its proposed partial privatisation of the NSW electricity network businesses.

In April the regulator said its decision would lead to savings on  electricity bills in 2015-16 of $165 for Ausgrid customers, $106 for Endeavour Energy customers and $313 for Essential Energy.

But it prompted a furious response from Vince Graham, the chief executive of Networks NSW, which runs the companies.

Mr Graham has warned 2750 jobs would be cut and that it would affect the companies' capacity for bushfire mitigation and response times to natural disasters.

On Thursday Networks NSW said it would appeal the AER decision on operating costs which had been reduced by an average annual $324 million.

This was "due to the impact on vegetation and bush fire risk mitigation programs across the state and the AER's decision not to provide a workable transition plan to implement continuing efficiency improvements".

"The AER's final determinations imposed significant cuts to capital and operating programs and the revenue required to operate safe and reliable electricity networks in NSW," Mr Graham said.

"The board of each NSW network business has carefully considered the implications of the AER's final decisions and do not believe the AER has followed the National Electricity Rules designed to provide safe, reliable and affordable electricity to 3.3 million electricity consumers in NSW."

Mr Graham said legal appeals would  be lodged with the Australian Competition Tribunal on Thursday and the Federal Court by May 28.

Also on Thursday, the Public Interest Advocacy Centre announced a separate legal challenge to the AER determination in the Australian Competition Tribunal - the first time a consumer group has done so.

"We are taking this action because we believe the revenue granted to these businesses is excessive and therefore NSW consumers will be forced to pay too much for network services over the next four years," said PIAC CEO Edward Santow.

Energy Minister Anthony Roberts said the government "shares the objective of the AER in delivering a safe and reliable supply of electricity to the state's customers at the lowest sustainable cost".

An AER spokesman said the regulator "carefully considered the matters before us in reaching our decisions which we consider to be in the long term interests of consumers."

Opposition leader Luke Foley said: "By appealing the AER determination the Baird Government has chosen to back higher power prices for every household and business in NSW."