The company's full-year EBITDAF guidance remained at $570m, reflecting impacts of the Tilt Renewables and Trustpower retail acquisitions and excluding likely interim insurance payment arising from Kawerau station outage.
It had been a period of significant change for Mercury – including becoming New Zealand's largest wind generator.
Chief executive Vince Hawksworth said settlement of the Tilt transaction and the Turitea North wind farm reaching full generation, as well as the closeout of a legacy contact with Norske Skog, all shaped Mercury's half-year results as it positioned itself for growth.
"Within the last six months, Mercury has transformed from a company with no wind generation to the largest wind generator in New Zealand," Hawksworth said.
In August, Mercury completed the acquisition of Tilt's New Zealand wind farms, and within the remaining period progressively brought the Turitea North wind farm on stream.
Together the assets would significantly diversify Mercury's revenue streams.
The Turitea South wind farm is scheduled for completion in mid-2023, which will make Turitea New Zealand's largest wind farm.
Meanwhile, the acquisition of Trustpower's retail business would be another significant milestone for Mercury.
During the period Mercury also negotiated the early exit of a foundation hedge with pulp and paper company Norske Skog.
The settlement of the wider transaction and its associated accounting impacts reduced the half year's EBITDAF by $50m.
Mercury said exiting this contract allowed Mercury to recontract this volume at a price more reflective of the current market.
The half year's EBITDAF was $242m, $48m down on the prior year, recognising acquisition accounting for Tilt and the close-out of the Norske Skog contract.
Mercury acquired Tilt's New Zealand operations including future development options for $797m in August 2021, funded from the sale of its Tilt shareholding and a cash cost of $634m.
For the six months, Mercury said sustained dry conditions across the Waikato catchment reduced hydro generation.
The 44-day outage at Kawerau geothermal power station also extended into the start of the financial year and coincided with high spot prices.
Looking ahead, Mercury said the electricity sector faced challenges.
Commenting on decarbonisation, Chair Prue Flacks said balancing affordability and security would be a key consideration for the electricity sector.
"The market must continue to evolve for the next phase of the transition, keeping what is good but adapting to address new challenges including the need for rapid response peaking capacity. Mercury welcomes the opportunity to participate in this transition," she said.
She said regulatory uncertainty facing the sector was also a challenge.
"We agree with the Government's position that climate change must be a priority but are increasingly concerned about the potential for policy or regulatory change that unintentionally undermines this position and jeopardises New Zealand's decarbonisation goals," she said.
"A good example of this is our resource management system, which needs to support renewable generation development if we are to decarbonise at a pace that becomes more urgent by the day," she said.
Shares in Mercury last traded at $6.03 - unchanged from Monday's close.
