KEY POINTS:
Electricity sector experts will tomorrow consider whether emergency measures, including putting diesel generators on standby, should be put in place to help the country through winter.
Southern hydro lakes - which are used to generate about 70 per cent of the country's power - are already lower than the 80-year average and could be drained in six weeks in winter if there is no significant rainfall.
Both Niwa and the MetService are forecasting lower than average rainfall through late summer in the southern hydro catchments. If the lakes remain low by April, winter prospects could be grim.
"I must say most people in the industry are watching it [the weather] very closely - as closely as the Waikato dairy farmers." said Kieran Devine, general manager of Systems Operations for Transpower.
Container-size diesel generators were an option to supplement power in some areas and drawing power from gas turbines on barges was on the drawing board, although not this winter because of an 18-month delay in delivery from overseas.
Large users would be asked to reduce use when demand peaked, usually over a few days in mid-winter.
The National Winter Group has warned there could be power cuts this winter, mainly for residential consumers and due to generator or transmission equipment failure. The group will meet in Wellington tomorrow to finalise contingency planning which is also likely to include better generation and demand forecasting.
Power supplies are already tight because two of Contact's New Plymouth power stations are out of action - one permanently - and the capacity of the interisland link has been drastically cut. Hot, humid weather over the past fortnight forced Huntly power station to reduce generation to avoid discharging cooling water into the Waikato River when it is higher than 23C.
Devine said getting Pole One of the high voltage link partially restored to allow greater capacity to move power between the islands was crucial to alleviating pressure on the grid.
Pole One was taken out of service last September because insurers were concerned about the fire risk in ageing equipment. Devine said he was now a little more than 50 per cent confident insurance could be back in place by the end of March.
Hydro lake levels on Sunday were 78 per cent of average for this time of the year, down from 84 per cent a week earlier. Devine said lakes could fill to capacity with just a week to 10 days of steady rain. "Having been involved with this for 20 years I rarely make a comment before April 1 - we're just too far out to make a realistic call.
"Providing nothing else fails we should be able to get through - there'll be some volatility in prices as things wax and wane but if something else breaks it could be a different story."
The Electricity Commission - which provides the regulatory framework to guarantee reliable power supply - has been forced to run the expensive diesel-burning standby power station over the past fortnight.
Commission chairman David Caygill said there was no way to absolutely guarantee supply. "I want people to understand that there's no price we could sensibly pay that could guarantee security. This is a modern well-managed electricity system which doesn't mean t9he lights will never go out because, even if you duplicated every line in the country, you could imagine an event which took duplicate lines out simultaneously."
He added: "Nobody has a crystal ball - we don't know exactly what's going to happen day by day or week by week or what the lake levels are going to be but in system that is 60 per cent hydro based then we're dependent on how much it rains."
TrustPower has hydro power stations throughout the country and spokesman Graeme Purches said lake levels were lower than the company would like them. "The risk is higher than it normally is but TrustPower thinks with careful management we can get through it."
Large industrial users who bought power on the spot market were feeling the pain of price spikes but domestic users who had tariffs fixed for a year remained insulated for the time being, he said.
SUPPLY PRESSURE
* Interisland power transmission constrained.
* Contact's 380MW combined cycle Taranaki station out for maintenance.
* Contact's ageing 100MW New Plymouth station closed.
* Hot weather pushing up demand.
* Huntly power station generation cut back.
