Mercury energy customers could be in for near 10-percent price hikes

The company says gas and electricity prices will lift on average 9.7 percent across the board, from April.

It reflects an increase in lines and transmission charges - fuelled by rising costs and infrastructure needs - and a rise in wholesale electricity costs.

Chair, Scott St John, says operating conditions remain a challenge, but Mercury's continuing to invest in new and existing assets.

He says a recent one-billion-dollar investment in new renewables is progressing well.