Transmission body says its proportion of domestic power bills is small and any increase would be $1 a month.
Big rises in household power bills are largely because of higher charges from Transpower to recover the cost of recent national grid upgrades, says Prime Minister John Key.
But while Transpower confirmed it had increased charges, it says they should add little more than $1 a month, a fraction of the increases consumers are facing.
Consumers in Wellington and Auckland have recently been told by power companies, including Genesis and Meridian, of big increases in their daily fixed charges which are only partly offset by small decreases in per unit charges.
The net effect will be many households paying 7 to 8 per cent more for their power, although some face increases of up to 24 per cent.