Hydro power: More dry weather may mean blackouts, switch to coal-generated 29 Apr, 2021 01:34 AM 4 minutes to read Lake Pukaki right now. Photo / Matthew Clark RNZ By Charlotte Cook of RNZ National grid operator Transpower says the hydro lake levels are at 67 per cent of where they would normally be at this time of year, but there is no cause for worry yet. New Zealand's biggest energy consumer, the Tiwai Point aluminium smelter, today agreed to cut down how much power it uses for a month to secure supply for the country. The smelter consumes about 13 per cent of the country's power and it will reduce its hourly use by up to 30.5MW.