Transpower says an Antarctic blast this week could set an October record for electricity demand, but it expects the lights to stay on.

An icy front due from Wednesday will likely see people cranking up their heaters, with snow down to low levels in Canterbury, Otago, Southland and the lower North Island that night.

National grid operator Transpower says despite expecting a cold day even by winter standards there is enough supply to avoid power outages.

Longer sunshine hours and the fact it is school holidays could help ease the uptick in demand.

But there is uncertainty about the wind forecast which could affect output from turbines.

Transpower general manager operations Dr Stephen Jays says it will closely monitor the weather reports, and the amount of demand and supply of power.

It will issue a notice to industry requesting additional generation if needed.

Transpower says it has made changes since it was held responsible by the electricity watchdog for widespread outages on one of the coldest nights of last year.

-RNZ.