National controlled storage recovered following significant South Island rainfall in late March. In addition, 220GWh of stored water becomes available on 1 April as it changes from contingent storage (over summer) to active storage available to generation companies. On 29 March the system operator updated the hydro risk curves, raising them slightly. Each update to the 2019 HRCs is presented in a public dashboard on EMI. Official curves and more information on security of supply forecasting is available on the system operator's website.

October 2018 was a period of low inflows and reduced thermal fuel availability that resulted in sustained high prices. Several participants joined forces to lodge an Undesirable Trading Situation (UTS) claim in relation to the circumstances and information available to market participants at this time. Taupo inflows have been low since late September 2018, (74 per cent of average from 1 Oct 2018 to 15 Jan 2019) contributing to national controlled storage remaining below average. As 2019 gets underway, prices continue to remain stronger than in recent years.

Late in 2018 New Zealand Aluminium Smelters restarted the fourth potline at Tiwai Point after securing supply for an additional 50 MW of electricity through to December 2022 from Meridian. The potline was last in operation back in 2012. The daily energy demand at the Tiwai node has increased by more than seven per cent reflecting this change in operation.