Two of Contact Energy's big gas fired power stations are out of operation, at the same time Mighty River Power's gas fired Southdown is also out for "routine" maintenance, taking capacity equal to almost 1000 megawatts out of the market at the same time.
The plants are out at the same time as Taranaki's veteran Maui gasfield is shut down for a major month-long maintenance project that will involve at least 265 workers.
The shutdown of big North island stations means wholesale electricity prices are up even though hydro power lake levels are 111 per cent of average for the time of year and lakes have been well above average for many months.
Contact Energy said yesterday that: "TCC (Taranaki Combined Cycle) in Stratford is effectively on an outage - we've discovered an issue which requires remedying and so we're currently choosing not to run the plant."
Contact also said its Otahuhu plant in Auckland was not running, either. The two plants account for about a third of Contact's installed capacity.
"Market conditions and fuel positions haven't supported us running Otahuhu, so we've elected not to run it and instead utilise other generation options," Contact corporate communications manager Shaun Jones said.
The Taranaki Combined Cycle Power Station is a large plant, capable of producing 377 megawatts of electricity.
"There's a minor internal defect with the TCC plant that it has run with in the past - we're taking the opportunity to repair it on a scheduled outage in the summer months, as we normally would do," the spokesman said. The plant would be back on March 7.
Otahuhu B in Auckland is a 400MW power station, and its return would depend on market conditions. "The large (combined cycle) CCGTs are more expensive to run that other generation options such as geothermal, hydro," Jones said.
MRP said yesterday that Southdown was not dependent on Maui gas alone, but some other generators depend totally on Maui gas so the field's shutdown would affect their ability to produce from gas-fire plants.
With the Maui gas field out and a lack of wind on some days, wholesale power prices had been "whippy", one power company executive said yesterday.
Late yesterday, wholesale market prices were about $85 a megawatt hour in the upper North Island, but had been above $120 a unit earlier in the day, about twice the levels seen in late January.
The giant gas field - comprising the Maui A and B offshore platforms and the Oaonui onshore production station - was shut down on Saturday for the project, which will have contractors working on site 24 hours a day, seven days a week.
Operator Shell Todd Oil Services (Stos) said the project had been planned for a time when the halt to gas from the field, which supplies about 20 per cent of New Zealand's needs, will have the least impact on the market.
"February is traditionally a period of low natural gas demand and good weather for the maintenance programme, " said Stos general manager Rob Jager.
Meanwhile, Mighty River Power's gas-fired 175 megawatt Southdown power station in Auckland is out of action for maintenance for another six weeks.
MRP chief executive Doug Heffernan said the wholesale electricity market had been informed of the plan to shut Southdown late last year. The plant was 17 years old, so needed money spent on it routinely, he said.
"There has been a lot of water around for 18 months and we decided we'd take Southdown down at the end of last year . . . Southdown is no baby and needs some TLC" Heffernan said.
MRP was doing "running repairs" on Southdown, which would be back on the market in mid to late March.
The best time to run Southdown was during winter when power demand was high. At the current market prices of about $100 a unit, Southdown did not make money, Heffernan said.
Southdown has produced less than 5 per cent of MRP's total generation in the past few years.