The error resulted in the setting of revenue targets higher than they should have been between 2015 and 2023, leading to non-deliberate over-charging of the lines component of electricity bills.
Alpine Energy chair Melissa Clark-Reynolds said the regrettable error was discovered in the 2023 audit and would be fixed in a transparent, timely and practical way.
The error meant Alpine was billing retailers based on revenue forecasts which were higher than they ought to have been.
Ms Clark-Reynolds said network costs formed about 27% on average of a customer’s power bill.
"Our current estimate is that this translates to network charges being overcharged by around 3%. So as a result, our 33,500 customers have on average been paying about 1% more for their electricity than they should have.
"Going forward, Alpine will work with the Commerce Commission to finalise the assessment and the method for correcting this over charging.
“The complexity of the financial models used to regulate the sector make it a challenging task to precisely establish the overcharged amount.
"This will need to be worked through with the commission."
She said an early estimate suggested this would amount to an average of about $2million per year, 3% of Alpine’s total revenue for the nine-year affected period.
“While we still have much to work through with the commission, we have taken some initial actions.
"Alpine has decided to correct its planned 2024/25 lines charge revenue by about 6%. This will offset the 9% average increase in lines charges which we had previously notified.
"These lower-then-previously notified charges will apply until March 31, 2025.
"Alpine is intending to make the correction before winter."
The board had also decided it would not pay an interim dividend for the three months ending March 2024.
“It is unfortunate this accounting error has occurred, but I can assure our customers, shareholders and other stakeholders that the board is working towards a fair and pragmatic resolution,” Ms Clark-Reynolds said.
