Mighty River Power says it is well set up for entering the summer period, with hydro volumes in Taupo above average for this time of year.
Electricity sales fell 5% for the first quarter, compared with the same period last year, partly due to an 8% drop in commercial volumes, largely because of when commercial contracts fall.
Overall generation volumes fell 18%, with hydro generation at its lowest level for a first quarter in the company's history.
Mighty River Power chief executive Doug Heffernan says the weak inflow into the Waikato catchment made it a challenging quarter, but that was offset by the geothermal contribution, which made up more than 40% of the total supply.
He says the last quarter's performance has vindicated the company's diversification strategy which it launched five years ago, with the $1.4 billion investment in geothermal, which provided Mighty River Power with resilience during a time of low hydro inflows.