Quarterly Operational Update

4Q-FY26 Trading update for the three months ended 30 June 2026. QUARTERLY HIGHLIGHTS > All turbines at Kaiwera Downs Stage 2 Wind Farm are installed with reliability testing underway. We expect all turbines to be handed over by the end of August. > Kaiwaikawe Wind Farm progressing on schedule and expected to be fully operational in H1 FY27. First generation from 6 installed turbines started on time in July. Our WindPlatform underpins the delivery of our wind projects at scale, on time and on budget. > Fast-track consent granted for Puke Kapo Hau Wind Farm, reinforcing Mercury’s renewable development pipeline and future growth options. > Launched Flex Rates, our new Time of Use electricity plans for eligible retail customers, giving more control over their electricity costs. MERCURY DELIVERS STRONG Q4 PERFORMANCE Mercury delivered a strong fourth quarter, with higher renewable generation and disciplined portfolio management supporting trading margin of $390m, up 33% on PCP. The quarter also reflects continued delivery across our renewable development and asset renewal programmes, with major milestones achieved across Kaiwera Downs, Kaiwaikawe and our hydro refurbishment programme. Overall, this performance highlights strong operational momentum and disciplined execution against our strategic priorities. Our May Geothermal Investor Day demonstrated the scale of Mercury’s geothermal platform, with more than 1TWh entering feasibility and $75m committed to appraisal drilling at the Ngā Tamariki and Rotokawa geothermal fields. Together, these milestones conclude a year of strong operational delivery across Mercury’s renewable development and asset renewal programmes. - Mercury Chief Executive Stew Hamilton Trading Margin $390m > Up 33% on PCP > Up $97m on PCP > YTD Trading margin up $269m to $1,421m Generation Volume 2,344GWh > Up 339GWh on PCP > YTD Generation volume up 1,163Gh to 9,070GWh Hydrological Inflows 61st percentile > Down from 79th percentile PCP > YTD Inflows were at 83rd percentile compared to 12th percentile PCP [For Operational Statistics and Charts, please refer to the attachment] ENDS Howard Thomas General Counsel and Company Secretary Mercury NZ Limited For investor relations queries, please contact: Paul Ruediger Head of Business Performance & Investor Relations 027 517 3470 investor@mercury.co.nz For media inquiries, please contact: Catherine Morab External Communications Manager 09 282 1158 mercurycommunications@mercury.co.nz