Contact Energy (ASX:CEN, NZE:CEN) accepted a draft determination from New Zealand's Electricity Authority that it was responsible for an under-frequency event that occurred in December 2025, the regulator said Tuesday.

The event involved Contact Energy's Tauhara generator tripping, which reduced North Island frequency to 49.225 hertz.

The Tauhara TAB G1 electricity generation unit tripped due to the activation of turbine differential expansion protection, with the system operator's report identifying Contact Energy as the causer, the Electricity Authority said.

The event charge calculated in the operator's report is NZ$136,700, and the clearing manager will rebate the event charges to the relevant participants.

Contact Energy did not immediately respond to a request for comment from MT Newswires.

The company's New Zealand and Australian shares each gained 1% in recent Tuesday trade.