Staff will monitor energy consumption at 15 substations across Newcastle leading up to 8.30pm and beyond.

The data, which will be reported in Monday's Herald, will provide the clearest possible indication of how much power was saved during Earth Hour.

EnergyAustralia spokesman Allyn Hamonet said it was essential that Earth Hour was compared with similar periods to achieve a meaningful result.

"The results are corrected for changes in weather, economic growth and daylight savings and then compared to average hourly electricity use from a collection of Saturdays during the same month," he said.

The region's power consumption fell from an average baseline of 531.01 megawatt hours to 508.4 megawatt hours, a 4.3 per cent reduction, during last year's Earth Hour.

But several parts of Newcastle registered an increase in energy consumption, largely as a result of industrial demand.

Mr Hamonet said a similar result might occur this year.

"Demand on the Broadmeadow substation has grown in the past year because of an expansion in commercial activity in the area," he said.

"You also need to take into account things like the Newcastle Show."