Concerns bad investment choices in electricity generation will keep our supply unreliable

Tiwai Point aluminium smelter is ramping up production reversing previous restrictions, to ease winter supply concerns.

Meridian Energy says the hydro storage is looking much healthier this winter.

Major Electricity Users' Group Chair John Harbord says restrictions will likely be back in force next winter, without investment in firmer electricity supply, like geothermal and hydro plants.

He says solar panels only generate electricity 25 percent of the time and wind turbines only create energy 40 percent of the time.