Quarterly Operational Update

1Q-FY27 Trading update for the three months ended 30 September 2026. QUARTERLY HIGHLIGHTS > Kaiwera Downs Stage 2 has reached full generation. The $486 million expansion project was completed in two years, adding 36 turbines and 155MW of installed capacity. > All 12 turbines now installed at Kaiwaikawe Wind Farm. The wind farm began generating in July, reflecting the pace and strength of our construction delivery. > Puke Kapo Hau Wind Farm is progressing to plan, with works expected to begin in November 2026. > FY27 SIB CAPEX is expected to be around $150m, with growth CAPEX expected to be between $300m and $400m. > This year also marks 25 years of partnership with Starship. Since 2001, Mercury and its customers have raised more than $20 million to support the care of children and families across New Zealand, and we are proud of what our partnership has achieved. MERCURY DELIVERS STRONG Q1 PERFROMANCE Mercury delivered a strong first quarter, with trading margin of $445 million, up 19% on PCP, despite Waikato hydro inflows at the second percentile. This demonstrates the resilience of our earnings, supported by disciplined portfolio management and our diversified generation portfolio. We continue to deliver against our renewable development programme, while maintaining our focus on disciplined investment and funding growth on balance sheet within our financial guardrails. Based on our current outlook, we remain on track to deliver our FY27 EBITDAF guidance. - Mercury Chief Executive Stew Hamilton Trading Margin $445m > 19% on PCP > $70m on PCP > YTD Trading margin up $70m to $445m Generation Volume 2,526GWh > 26GWh on PCP > New wind and geothermal generation (up 307GWh) offset by lower hydro volumes, down 332GWh or 24% Hydrological Inflows 2nd percentile > from 71st percentile PCP > YTD Inflows were at 2nd percentile compared to 71st percentile PCP 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