Trustpower's profit for the past six months was $33.6 million, down 13 percent from a year ago.
The decrease was caused by severe droughts, a fall in the amount of power produced, and by Covid-19 disruptions.
However, the retail side of the business contributed to overall growth of 3 percent in underlying earnings.
Trustpower chief executive David Prentice said the result was pleasing, considering three main challenges during the period.
"You need to put that into context of the last six months... there was obviously the ongoing impacts of Covid, we are also navigating what has turned out the be an incredibly dry last six months with some even calling it the equivalent of a 100-year drought.
"And of course there are many ongoing challenges within the electricity sector," Prentice said.
Trustpower also offered telco services and its diverse portfolio had helped mitigate the loss from lower power generation levels, he said.
Prentice predicted the closure of Tiwai Point smelter would lead to an initial drop in demand that would create volatility, but the market would level out.
"The market has been anticipating this for a number of years... there will be a short to medium-term impact but the electricity market in New Zealand is incredibly robust and it will go through a period of uncertainty, but re-balance after that."
Trustpower took an increased provision to bad debts at the start of the year, but collection levels remained business-as-usual.
Guidance for the full year had dropped slightly, with EBITDAF projected to be between $185m and $205m
"That's really to reflect the incredibly dry conditions around the country and our forecast for generation, which has dropped as a result of that.
"Other than that, I remain optimistic that we are operating within a very robust sector."