Mighty River Power's quarterly electricity sales have risen by 12%, boosted by a jump in commercial volumes.
The electricity generator and retailer will be the first of the state-owned companies the Government puts up for partial sale.
Sales volumes rose to 1,359 gigawatt hours in the three months to June, with demand from commercial customers rising by 29% compared with the same period a year earlier.
Customer numbers fell 2% to 396,000.
Wholesale purchase costs more than doubled due to lower hydro inflows into southern lakes.
The company's generation volumes fell 8%, with hydro down a quarter because of lower inflows into the Waikato River.