WELLINGTON, New Zealand--Power company Mercury Ltd. said its full-year earnings will be less than previously forecast because of lower hydro generation and an outage at a geothermal power plant that it expects to last months.

The New Zealand company said Wednesday it expects operating earnings of 460 million New Zealand dollars ($331 million) for its 2021 financial year. Its previous forecast was NZ$520 million.

Hydro generation is expected to decline by 200 gigawatt hours to 3,600 GWh for the full financial year due to dry weather lowering lake levels, Mercury said.

Earnings would also be hit by a mechanical failure at the Kawerau geothermal power station that began June 7 and could last for several months. Costs would be partly covered by business interruption insurance, Mercury said.

Write to Stephen Wright at stephen.wright@wsj.com

(END) Dow Jones Newswires

06-08-21 1713ET