Npower, the retail arm of the UK's largest electricity supplier, RWE npower, is consolidating the details of its six million residential customers onto a single database.
The company, which was formed in 2000 through a merger of several utility companies, recently completed the migration of six million customer accounts to a single billing and accounting system.
In recent weeks, however, customers have been unable to resolve account queries. Call centre operators said they were unable to access the database from the main billing system because connectivity was "continually going up and down".
An npower spokesman said, "As with any large migration there have been some issues. However we are addressing these and we are confident that the end result will allow us to provide a better service for our customers."
Npower has consolidated its customers into the bespoke dual-fuel system used by Northern Electric, which merged with Npower in 2000.
The company chose this as the main billing system because it was a fully featured program that required little development to support npower's customers.
The energy company said moving the customer information to a single database was expected to enable it to provide consistent customer services and help speed up the development of new products.
Longer term benefits will include reduced training times and the ability to further optimise business processes easily by having all the customer data in one place.