A lack of rain has left South Island lake levels very low, with wholesale electricity prices expected to climb as power producers hold crisis meetings.
Transpower chief executive Alison Andrews says water inflows have only been 56 per cent of the average since March 2017.
"Prices have increased as fuel has become scarce - less water - and so people who are paying spot prices will be paying higher prices at these times," she says.
With no significant rainfall forecast, power grid company Transpower called an industry-wide conference in Wellington yesterday.
Energy analyst Molly Meluish said electricity generators were not doing enough, that spot price users played the system by using more power at night when power prices are cheapest, but recently night time prices have started to go up.
"I used to turn the hot water on at night, only I don't now - it's not worth it ... the network prices are not reflecting the actual level of demand on their system," she says.
She expects those on fixed plans will also see higher bill next winter.
While Ms Andrews says: "We think we will ride through and recover - but it's very early days to predict".
So what can be do to avoid a bill shock?
"Use fire wood if you can, that's what I'm doing and I'm keeping my bills low".