Quarterly Operational Update

Quarterly Operational Update for the three months ended 31 March 2025. QUARTERLY HIGHLIGHTS > FY25 HYDRO GENERATION FORECASTED TO BE 3,400 GWH - from record low Q3 hydro inflows in the Waikato catchment. > LONG TERM AGREEMENT SIGNED WITH FONTERRA - agreement for ~260GWh signed for Waitoa and Edgecumbe sites. > NZAS SUPPLY AGREEMENT TAKES EFFECT - end user CFD agreement with New Zealand Aluminium Smelters commenced this quarter. COMMENTARY MARKET SUMMARY National hydrological inflows were the lowest on record during the quarter, resulting in high spot electricity prices averaging $225/MWh in Auckland. Forward prices remain high at $205/MWh in Auckland for financial years 2025 to 2027 as of 31st March 2025. Normalised national demand was 3.5% lower for the quarter relative to PCP, mainly impacted by irrigation and industrial demand response.  RECORD LOW Q3 WAIKATO CATCHMENT INFLOWS AND DECREASED WIND SEES LOWER GENERATION OUTPUT  Waikato catchment inflows were the lowest on record over the quarter which saw Q3 hydro generation reduce to 710GWh (-295GWh, 29% lower than PCP). 3rd percentile inflows in the Waikato catchment over the past nine months has resulted in 2,547GWh of hydro generation (-530GWh, 17% lower on PCP). We are forecasting 3,400GWh of hydro generation for the full year, due to the continued dry conditions since the start of the financial year. Lower average wind speeds over the quarter saw 373GWh of wind generation (-144GWh, 28% lower than PCP). Geothermal generation was 35GWh lower than PCP at 629GWh driven in part by a planned maintenance outage at the Ngā Tamariki generation site. LONG TERM AGREEMENT SIGNED WITH FONTERRA Mercury has agreed a long-term contract with Fonterra to support the electrification of their Edgecumbe and Waitoa operations. The supply agreements extend for ten years for each site, with Waitoa commencing from Aug-25 and Edgecumbe from Jul-26. This represents total demand of ~260 GWh per year, weighted towards summer quarters. NZAS SUPPLY AGREEMENT COMMENCED THIS QUARTER The long term supply agreement with New Zealand Aluminium Smelters has taken effect from Jan-25. This end user contract for difference agreement is initially for 50MW, stepping up to 75MW in 2027. [For Operational Statistics and Charts, please refer to the attached] 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 queries, please contact: Shannon Goldstone Reputation and Social Impact Lead 027 210 5337 mercurycommunications@mercury.co.nz