Alderney Airport overcharged £114,000 for electricity
Alderney Airport was overcharged £114,000 for electricity between 2006 and 2012 by Alderney Electricity.
The firm said a "clerical error" meant Guernsey States, who are responsible for the airfield, were overcharged.
Alderney Electricity chairman Mike Richards apologised and said the bill for the States was charged monthly but was duplicated each quarter.
He said the problem came to light in mid-May after new management reporting systems were set up.
Mr Richards said the company had carried out an internal inquiry to find out how the error arose.
He said he had discussed with Guernsey's Treasury and Resources Department about how to repay the money.
Mr Richards said: "It is an historic situation which arose from a clerical error made before any of the current board or employees were in post.
"We are satisfied all payments received from the States of Guernsey can be accounted for and no impropriety has taken place."